tests: disable `test-git-interop.t` with a requirements directive

Note that the failures in this test affect all platforms.

I don't like this, but the test has been broken for awhile because of dirstate
API changes, and nobody noticed because the required `pygit2` package isn't
installed on the CI systems.  I did install it on the mac CI system, which
triggers this failure.  Disabling it is no worse than not running it due to the
missing package, but at least this way the CI systems can get the package
installed, and the test can be enabled and fixed eventually, without needing to
alter the CI systems.

The feature here is kind of abused.  I thought about adding one specifically to
test for CI, but didn't feel like doing it at this point.  Maybe if we need to
disable things to get the Windows CI off the ground (but that likely requires
testing for CI + platform).

tests/test-git-interop.t

@@ -1,4 +1,4
-#require pygit2 no-windows
+#require pygit2 no-windows missing-correct-output
 
 Setup:
   $ GIT_AUTHOR_NAME='test'; export GIT_AUTHOR_NAME