[generic] Skip Test_Generic25, it changes frequently

But it was only added 2 weeks ago by @dstftw in
b68a812ea839e44148516a34a15193189e58ba77, so maybe it should be
handled differently? Remove the test? Mark it only_matching? Not sure.

youtube_dl/extractor/generic.py

@@ -465,6 +465,7 @@ class GenericIE(InfoExtractor):
             'params': {
                 'skip_download': True,  # m3u8 download
             },
+            'skip': 'video rotates...weekly?',
         },
         {
             # Brightcove:new type [2].