test: enable sparse-revlog for test-narrow-clone-stream.t

We are about to enable sparse-revlog globally. To help with reviewing the
tests change, we isolate them in individual changesets.

Differential Revision: https://phab.mercurial-scm.org/D5326

tests/test-narrow-clone-stream.t

@@ -1,3 +1,9 b''
+TRANSITIONAL CONFIG
+  $ cat << EOF >> $HGRCPATH
+  > [format]
+  > sparse-revlog = yes
+  > EOF
+
 #testcases tree flat-fncache flat-nofncache
 
 Tests narrow stream clones
@@ -66,6 +72,7 b' Making sure we have the correct set of r'
   generaldelta
   narrowhg-experimental
   revlogv1
+  sparserevlog
   store
   treemanifest (tree !)