py3: remove unneeded fsencode() from gitsubrepo

Here p.stdout isn't a TextIO. read() must return bytes.

mercurial/subrepo.py

@@ -1286,7 +1286,7 b' class gitsubrepo(abstractsubrepo):'
         if stream:
             return p.stdout, None
 
-        retdata = pycompat.fsencode(p.stdout.read().strip())
+        retdata = p.stdout.read().strip()
         # wait for the child to exit to avoid race condition.
         p.wait()