Merge branch 'js/no-more-prepare-for-main-in-test'

Test coverage fix.

* js/no-more-prepare-for-main-in-test:
  tests: drop the `PREPARE_FOR_MAIN_BRANCH` prereq
  t9902: use `main` as initial branch name
  t6302: use `main` as initial branch name
  t5703: use `main` as initial branch name
  t5510: use `main` as initial branch name
  t5505: finalize transitioning to using the branch name `main`
  t3205: finalize transitioning to using the branch name `main`
  t3203: complete the transition to using the branch name `main`
  t3201: finalize transitioning to using the branch name `main`
  t3200: finish transitioning to the initial branch name `main`
  t1400: use `main` as initial branch name