View Commits : Missing label for show and hide commit graph button.

Issue Summary

In the View commits page the button to show and hide the commit graph has a missing label.

Steps to Reproduce

1. Launch the URL
2. Navigate to the "Show the commit graph" or "Hide the commit graph" in the main content area beside the commits 

Screenshot

Actual Results

"Show the commit graph" and "Hide the commit graph" buttons do not have a label associated with it. When screen readers reach this button with no label they announce the "button Press enter to activate” button. Blind users will be unable to identify the purpose of this button.

Expected Results

Add a descriptive label for the button via the aria-label attribute. For example, provide the label as “Hide Commit Graph” or "Show Commit Graph".

Workaround

Currently, there is no known workaround for this behaviour. A workaround will be added here when available.

Bug Ref: 740750