Merge branch 'develop-remove-forall'. Close #518.

**Description**

The function `Copilot.Language.Spec.forall` was deprecated due to the
function name not being allowed in newer versions of GHC. An alternative
was provided, so the old function is not being used by any part of
Copilot.

The original functions was deprecated in Copilot 3.18 and no messages
have been received requesting that they be kept in this library.

As per our internal policy of waiting 3 versions from deprecation until
a public interface declaration can be removed, these functions can now
be removed.

**Type**

- Bug: unused code included in the implementation.

**Additional context**

- Issue #470  , addressed in Copilot 3.18, deprecated the function.

**Requester**

- Ivan Perez

**Method to check presence of bug**

Although this is not a bug per se, compiling with GHC >= 9.4 and
--ghc-options='-Werror=forall-identifier' produces an error due to
including a function called `forall`, which is not allowed in new
versions of GHC.

The following dockerfile installs copilot with GHC 9.8 and
`--ghc-options='-Werror=forall-identifier'`, and prints the message
"Success" if installation completes:

```Dockerfile
FROM ubuntu:focal

ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get update

RUN apt-get install --yes libz-dev
RUN apt-get install --yes git

RUN apt-get install --yes wget
RUN mkdir -p $HOME/.ghcup/bin
RUN wget https://downloads.haskell.org/~ghcup/0.1.19.2/x86_64-linux-ghcup-0.1.19.2 -O $HOME/.ghcup/bin/ghcup

RUN chmod a+x $HOME/.ghcup/bin/ghcup
ENV PATH=$PATH:/root/.ghcup/bin/
ENV PATH=$PATH:/root/.cabal/bin/
RUN apt-get install --yes curl
RUN apt-get install --yes gcc g++ make libgmp3-dev
RUN apt-get install --yes pkg-config

SHELL ["/bin/bash", "-c"]

RUN ghcup install ghc 9.8.2
RUN ghcup install cabal 3.2
RUN ghcup set ghc 9.8.2
RUN cabal update

SHELL ["/bin/bash", "-c"]
CMD git clone $REPO && cd $NAME && git checkout $COMMIT && cd .. \
  && cabal v1-sandbox init \
  && cabal v1-install alex happy \
  && cabal v1-install --ghc-option="-Werror=forall-identifier" $NAME/**/ \
  && echo "Success"
```

Command (substitute variables based on new path after merge):
```
$ docker run -e "REPO=https://github.com/Copilot-Language/copilot" -e "NAME=copilot" -e "COMMIT=<HASH>" -it copilot-verify-518
```

**Expected result**

Running the dockerfile above prints the message success, indicating that
Copilot does not define the identifier `forall` anywhere.

**Solution implemented**

Remove the deprecated function `Copilot.Language.Spec.forall`, and any
references to it (exports).

Adjust README to indicate that copilot now compiles with GHC 9.8.

**Further notes**

None.

Author: ivanperez-keera

copilot-language/CHANGELOG

@@ -1,3 +1,6 @@
+2024-07-06
+        * Remove deprecated function Copilot.Language.Spec.forall. (#518)
+
 2024-05-07
         * Version bump (3.19.1). (#512)
 

copilot-language/src/Copilot/Language.hs

@@ -38,7 +38,7 @@ module Copilot.Language
   , prop
   , theorem
   , forAll
-  , forall, exists
+  , exists
   ) where
 
 import Data.Int hiding (Int)

copilot-language/src/Copilot/Language/Spec.hs

@@ -28,7 +28,7 @@ module Copilot.Language.Spec
   , prop, properties
   , theorem, theorems
   , forAll
-  , forall, exists
+  , exists
   , extractProp
   , Universal, Existential
   ) where
@@ -165,11 +165,6 @@ data Prop a where
 forAll :: Stream Bool -> Prop Universal
 forAll = Forall
 
-{-# DEPRECATED forall "Use forAll instead." #-}
--- | Universal quantification of boolean streams over time.
-forall :: Stream Bool -> Prop Universal
-forall = forAll
-
 -- | Existential quantification of boolean streams over time.
 exists :: Stream Bool -> Prop Existential
 exists = Exists

copilot/CHANGELOG

@@ -1,3 +1,6 @@
+2024-07-06
+        * Update README to reflect support for GHC 9.8. (#518)
+
 2024-05-07
         * Version bump (3.19.1). (#512)
 

copilot/README.md

@@ -81,7 +81,7 @@ ghci> ghci> Leaving GHCi.
 On other Linux distributions or older Debian-based distributions, to use
 Copilot you must install a Haskell compiler (GHC) and the package manager
 Cabal. We currently support all versions of GHC from 8.6.5 to modern versions
-(9.6 as of this writing). You can install the toolchain using
+(9.8 as of this writing). You can install the toolchain using
 [ghcup](https://www.haskell.org/ghcup/) or, if you are on Debian/Ubuntu,
 directly with `apt-get`: