tests: add b'' to notcapable

This fixes some exceptions in a few tests.

# skip-blame just b'' prefixes

Differential Revision: https://phab.mercurial-scm.org/D5646

tests/notcapable

@@ -11,7 +11,7 def extsetup(ui):
     extensions.wrapfunction(repository.peer, 'capable', wrapcapable)
     extensions.wrapfunction(localrepo.localrepository, 'peer', wrappeer)
 def wrapcapable(orig, self, name, *args, **kwargs):
-    if name in '$CAP'.split(' '):
+    if name in b'$CAP'.split(b' '):
         return False
     return orig(self, name, *args, **kwargs)
 def wrappeer(orig, self):