Why:

Closes: #43081

What's being changed (if available, include any code snippets, screenshots, or gifs):

workflow_dispatch is absolutely able to be triggered when the workflow file is not in the default branch. The issue lies in HOW it can be triggered: when it is in the default branch, the Github UI can be used. When it is not, then the Github UI cannot be used. The "Note" regarding this should be updated, as it misleads the reader into thinking that workflow_dispatch is more limited than it is.

Please also refer to the Issue linked above.

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.