Remove AVR test build

Author: dhardy

.github/workflows/test.yml

@@ -154,18 +154,6 @@ jobs:
       - name: Build top-level only
         run: cargo build --target=thumbv6m-none-eabi --no-default-features
 
-  # Disabled due to lack of known working compiler versions (not older than our MSRV)
-  # test-avr:
-  #   runs-on: ubuntu-latest
-  #   steps:
-  #     - uses: actions/checkout@v4
-  #     - name: Install toolchain
-  #       uses: dtolnay/rust-toolchain@nightly
-  #       with:
-  #           components: rust-src
-  #     - name: Build top-level only
-  #       run: cargo build -Z build-std=core --target=avr-unknown-gnu-atmega328 --no-default-features
-
   test-ios:
     runs-on: macos-latest
     steps: