[7.2.0] Always create an empty MODULE.bazel for python tests (#22097)

To prevent python tests from accessing BCR, this was missed in
https://github.com/bazelbuild/bazel/commit/055e25b75c74d1e2c4c71694a938b6456323facc

Closes #22089.

PiperOrigin-RevId: 627384354
Change-Id: Ic4545616fad88f479b24553eb7ffe81004d41090

Commit
https://github.com/bazelbuild/bazel/commit/c900865bbb3c38b589d6e5fbc422d61d3bba4681



Co-authored-by: Yun Peng <pcloudy@google.com>