rebase_and_merge_summary: correct link description to git-scm.com/docs

The text links to the official documentation for `git rebase` at 
https://git-scm.com/docs/git-rebase, but mislabels the link as a chapter 
in the "Pro Git" book.

Fix that.

Author: phil-blain

data/reusables/pull_requests/rebase_and_merge_summary.md

@@ -2,6 +2,6 @@ When you select the **Rebase and merge** option on a pull request on {% data var
 
 To rebase and merge pull requests, you must have [write permissions](/articles/repository-permission-levels-for-an-organization/) in the repository, and the repository must [allow rebase merging](/articles/configuring-commit-rebasing-for-pull-requests/).
 
-The rebase and merge behavior on {% data variables.product.product_name %} deviates slightly from `git rebase`. Rebase and merge on {% data variables.product.prodname_dotcom %} will always update the committer information and create new commit SHAs, whereas `git rebase` outside of {% data variables.product.prodname_dotcom %} does not change the committer information when the rebase happens on top of an ancestor commit. For more information about `git rebase`, see [the "Git rebase" chapter from the _Pro Git_ book](https://git-scm.com/docs/git-rebase).
+The rebase and merge behavior on {% data variables.product.product_name %} deviates slightly from `git rebase`. Rebase and merge on {% data variables.product.prodname_dotcom %} will always update the committer information and create new commit SHAs, whereas `git rebase` outside of {% data variables.product.prodname_dotcom %} does not change the committer information when the rebase happens on top of an ancestor commit. For more information about `git rebase`, see [the official Git documentation](https://git-scm.com/docs/git-rebase).
 
 For a visual representation of `git rebase`, see [The "Git Branching - Rebasing" chapter from the _Pro Git_ book](https://git-scm.com/book/en/Git-Branching-Rebasing).