Super-Linter should run on pull requests to branches other than Main

[jongalloway]

We generally create a branch for all the release notes for a release. For instance, we created a branch for .NET 10 Preview 7 called dotnet10-p7 and created one main pull request for the release notes (#10006). We also created multiple independent pull requests for each area, like #10000 for libraries which was on branch dotnet10-p7-libraries. Our workflow was to merge all of the area pull requests into the main dotnet10-p7 branch, and to merge that last.

The current linting action in https://github.com/dotnet/core/blob/main/.github/workflows/super-linter.yml only runs on pull requests to the main branch, so the final merge caught a lot of new issues. We need this linting action to run on all pull requests. I believe we are already doing this for the https://github.com/dotnet/core/blob/main/.github/workflows/markdown-link-check.yml action.