Fix predictive test source patterns

What does this MR do and why?

Fix predictive test source patterns.

Very easy to miss. I know.

How to set up and validate locally

Run scripts/verify-tff-mapping in this merge request, and it can show the following before fixing them:

Suspicious metacharacter detected. Are these correct?
  db/structure.sql => Did you mean: db/structure\.sql
  data/whats_new/\w*.yml => Did you mean: data/whats_new/\w*\.yml
  doc/index.md => Did you mean: doc/index\.md
  ee/config/metrics/.*.yml => Did you mean: ee/config/metrics/.*\.yml
  config/feature_categories.yml => Did you mean: config/feature_categories\.yml
  app/finders/members_finder.rb => Did you mean: app/finders/members_finder\.rb
  app/finders/group_members_finder.rb => Did you mean: app/finders/group_members_finder\.rb

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.