Fix outdated UI references: Replace "Edit" button with pencil icon for changing PR base branches

[John-Youngblood]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/changing-the-base-branch-of-a-pull-request

What part(s) of the article would you like to see updated?

Step 3 text mentions clicking "Edit" and the associated screenshots shows an edit button, however this edit button no longer exists and is instead replaced by a pencil icon next to the issue title. When hovering over this pencil icon, the tooltip reads "Edit title", so it is not entirely clear that clicking this button will also allow changing the base branch. This article should be updated to reference that the pencil icon is what's needed to be clicked to allow editing the base branch and a new screenshot should be included to correctly represent this change.

Additional information

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