ci: do not skip tagged revisions in GitHub workflows

ci: do not skip tagged revisions in GitHub workflows

When `master` is tagged, and then both `master` and the tag are pushed,
Travis CI will happily build both. That is a waste of energy, which is
why we skip the build for `master` in that case.

Our GitHub workflow is also triggered by tags. However, the run would
fail because the `windows-test` jobs are _not_ skipped on tags, but the
`windows-build` job _is skipped (and therefore fails to upload the
build artifacts needed by the test jobs).

In addition, we just added logic to our GitHub workflow that will skip
runs altogether if there is already a successful run for the same commit
or at least for the same tree.

Let's just change the GitHub workflow to no longer specifically skip
tagged revisions.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>