doc: git-pull: clarify how to exit a conflicted merge

From user feedback:

- One user is confused about why `git reset --merge`
  (why not just `git reset`?). Handle this by mentioning
  `git merge --abort` and `git reset --abort` instead, which have a
  more obvious meaning.
- 2 users want to know what "In older versions of Git" means exactly
  (in versions older than 1.7.0). Handle this by removing the warning
  since it was added 15 years ago (in 3f8fc18)

Signed-off-by: Julia Evans <julia@jvns.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: jvns

Documentation/git-pull.adoc

@@ -36,15 +36,9 @@ There are 4 main options for integrating the remote branch:
 You can also set the configuration options `pull.rebase`, `pull.squash`,
 or `pull.ff` with your preferred behaviour.
 
-In Git 1.7.0 or later, to cancel a conflicting merge, use
-`git reset --merge`.  *Warning*: In older versions of Git, running 'git pull'
-with uncommitted changes is discouraged: while possible, it leaves you
-in a state that may be hard to back out of in the case of a conflict.
-
-If any of the remote changes overlap with local uncommitted changes,
-the merge will be automatically canceled and the work tree untouched.
-It is generally best to get any local changes in working order before
-pulling or stash them away with linkgit:git-stash[1].
+If there's a merge conflict during the merge or rebase that you don't
+want to handle, you can safely abort it with `git merge --abort` or `git
+--rebase abort`.
 
 OPTIONS
 -------