tests: synchronize `simplestorerevisiondelta` with modern `irevisiondelta`

I noticed these fields had been missing when I pasted the body of
`revlog.revlogrevisiondelta` here to pick up the correct type hints in the
previous commit.  Not sure how this got out of sync, and there's probably not a
way to enforce this with Protocol either, unless the base class uses
`@abstractproperty` or something (which introduced its own trickiness for the
subclasses IIRC).

tests/simplestorerepo.py

@@ -82,6 +82,8 class simplestorerevisiondelta(repositor
     baserevisionsize = attr.ib(type=Optional[int])
     revision = attr.ib(type=Optional[bytes])
     delta = attr.ib(type=Optional[bytes])
+    sidedata = attr.ib(type=Optional[bytes])
+    protocol_flags = attr.ib(type=int)
     linknode = attr.ib(default=None, type=Optional[bytes])