Fix validation GitLab exclude repos

Created by: rvantonder

The regex ^[\w-]+/[\w.-]+$ validates a GitLab repo to exclude, meaning

• only contain one slash (the ones with yellow underscores have multiple /)
• may not contain a period . in the first part of the path name

But, these are valid GitLab paths:

• path/to/repo (multiple slashes, subgroups)
• path.with.dot/repo (first part of path contains .)

So we need to weaken the validation of the current regex pattern.