Clarify removal for non-installed extras & optional groups (#6229)

[chimaerase]

Pull Request Check List

Resolves: #6229

• Added tests for changed code.
• Updated documentation for changed code.

I haven't exhaustively verified claims made in these very simple documentation additions, but tried to keep them limited in scope to my personal experience with 1.2. Hopefully they are quite easy to review by someone more familiar with the project. If nothing else, this is a straw man example of the type of additions I would find helpful.

[chimaerase]

pre-commit.ci autofix

[github-actions]

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[poetry-bot]

The backport to 1.2 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.2 1.2
# Navigate to the new working tree
cd .worktrees/backport-1.2
# Create a new branch
git switch --create backport-6432-to-1.2
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 06e61fae04320eb24f4132452ee6f20e3e9049a2
# Push it to GitHub
git push --set-upstream origin backport-6432-to-1.2
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.2

Then, create a pull request where the base branch is 1.2 and the compare/head branch is backport-6432-to-1.2.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.