CI: Don't add testing repo in mypy check
py3-gitlab is now in community: https://gitlab.alpinelinux.org/alpine/aports/-/commit/b470cf0780124804e17ce7510418b77640a42b0b
py3-gitlab is now in community: https://gitlab.alpinelinux.org/alpine/aports/-/commit/b470cf0780124804e17ce7510418b77640a42b0b