Changes

refactor(tekton/v1): change registry to tidbx in Tekton triggers for tidbx builds (#3944)

This pull request updates the registry used for image builds in the
Tekton pipeline configuration files for the GCP environment. The
registry is changed from `hub` to `tidbx` to ensure images are pushed to
the correct location.

Configuration updates:

* Updated the `registry` value in `git-create-tag-build-ng.yaml` to use
`us-docker.pkg.dev/pingcap-testing-account/tidbx` instead of `hub`.
* Updated the `registry` value in `git-push-branch-build-ng.yaml` to use
`us-docker.pkg.dev/pingcap-testing-account/tidbx` instead of `hub`.
 (commit: 7f0017b)