Update branch descriptions for e2e test workflows

[daledupreez]

Changes proposed in this Pull Request:

This PR is a follow-up to #4727, which added a new workflow to manually trigger e2e tests across branches. However, @diegocurbelo flagged some concerns with the descriptive text and the fact that we have two branch variables.

This PR addresses one aspect of the comment now that we have some runs in place. At present, I am still keeping the custom branch input, as I think we may have situations where we want to run workflow code from one branch (such as for a PR), but target code from another branch (generally the e2e tests). Regardless, the changes in this PR only update the description for the branch input to reflect that the code will default to the same branch as the workflow branch if no other value is specified.

Testing instructions

Inspection should be sufficient.

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• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

Changelog entry

• This Pull Request does not require a changelog entry. (Comment required below)

Changelog Entry Comment

Comment

No need for a changelog entry as this only impacts the field descriptions for manually running workflows in the GitHub UI.

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[diegocurbelo]

Thanks @daledupreez, LGTM.

[Mayisha]