[pre-commit] Add DOCKERFILES_INFO_REPO_PRIMARY_BRANCH

[mmhw]

Description

Customers running pre-commit and having the DEMISTO_DEFAULT_BRANCH environment variable set to "main" for
example receive the following error:

FileNotFoundError: file in https://raw.githubusercontent.com/demisto/dockerfiles-info/main/docker_images_metadata.json does not exist

In this case it is not necessary to use this variable but simply use master.

[github-actions]

Changelog(s) in markdown:

• Fixed an issue in the pre-commit command where if the DEMISTO_DEFAULT_BRANCH environment variable was set to something other than "master", the command would fail. #4325