This PR updates the Git documentation to accurately reflect the current
UI and removes inaccuracies introduced in earlier drafts.

**Changes:**

- **Added Word Diff setting location**: The `word_diff_enabled` setting
is accessible in the Settings Editor under **Languages & Tools >
Miscellaneous**, which wasn't documented.

- **Simplified Remotes section**: Removed claims about command palette
actions for managing remotes that don't exist. The section now
accurately describes the remote selector in the Git Panel.

- **Added File History section**: Combined two paragraphs that said the
same thing.
Release Notes:

- N/A

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Co-authored-by: Zed Zippy <234243425+zed-zippy[bot]@users.noreply.github.com>