test: only run ffmpeg tests on release versions

The CI breaking because some new format was added in the master branch
is pretty annoying so only run these on release versions that are known
to work to reduce some maintenance burden. Although why we even bother
with this is still a valid question.

test/meson.build

@@ -135,9 +135,9 @@ endif
 
 # Supported libavutil versions that work with these tests.
 # Will need to be manually updated when ffmpeg adds/removes more formats in the future.
-if libavutil.version().version_compare('>= 59.0.100')
+if libavutil.version().version_compare('>= 59.0.100') and libavutil.version().version_compare('<= 59.39.100')
     refdir = join_paths(source_root, 'test', 'ref', 'ffmpeg7')
-elif libavutil.version().version_compare('>= 58.27.100')
+elif libavutil.version().version_compare('>= 58.27.100') and libavutil.version().version_compare('< 59.0.100')
     refdir = join_paths(source_root, 'test', 'ref', 'ffmpeg6')
 endif