DOC: Remove CONTRIBUTING note about ApplyClangFormat action
DOC: Remove CONTRIBUTING note about ApplyClangFormat action

As of 2020-01-08, this action [currently does not work from forked
repositories](https://github.community/t5/GitHub-Actions/Token-permissions-for-forks-once-again/td-p/33839)
because the [*GITHUB_TOKEN* has limited
permissions](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/authenticating-with-the-github_token#permissions-for-the-github_token). Branches need to be created on the upstream repository.

hjmjohnson/ITK,malaterre/ITK,richardbeare/ITK,thewtex/ITK,richardbeare/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,InsightSoftwareConsortium/ITK,Kitware/ITK,thewtex/ITK,malaterre/ITK,LucasGandel/ITK,malaterre/ITK,Kitware/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,thewtex/ITK,BRAINSia/ITK,malaterre/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,richardbeare/ITK,Kitware/ITK,richardbeare/ITK,vfonov/ITK,thewtex/ITK,thewtex/ITK,BRAINSia/ITK,LucasGandel/ITK,Kitware/ITK,malaterre/ITK,Kitware/ITK,thewtex/ITK,LucasGandel/ITK,hjmjohnson/ITK,richardbeare/ITK,InsightSoftwareConsortium/ITK,hjmjohnson/ITK,hjmjohnson/ITK,hjmjohnson/ITK,BRAINSia/ITK,LucasGandel/ITK,LucasGandel/ITK,vfonov/ITK,BRAINSia/ITK,richardbeare/ITK,LucasGandel/ITK,vfonov/ITK,Kitware/ITK,malaterre/ITK,vfonov/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,BRAINSia/ITK,malaterre/ITK,vfonov/ITK,hjmjohnson/ITK,LucasGandel/ITK,malaterre/ITK,thewtex/ITK,hjmjohnson/ITK,malaterre/ITK,BRAINSia/ITK,Kitware/ITK