drop jgit BR on Fedora >= 35
    
    With the impending removal of a large chunk of the Java package set,
    jgit will become unavailable as a BuildRequires in Fedora soon.  Remove
    the build dependency on Fedora >= 35.
    
    As noted in 8faf622 (drop jgit BR on Fedora > 30, 2019-07-29), this
    affects 3 tests, 2 for packfile format (t5310-pack-bitmaps) and
    1 of ls-remote (t5512-ls-remote).