test: use both bundle formats in test-bookmarks-pushpull

It is valuable to have both formats tested.

tests/test-bookmarks-pushpull.t

@@ -705,7 +705,17 b' Local push'
 Using ssh
 ---------
 
-  $ hg push -B @ ssh
+  $ hg push -B @ ssh --config experimental.bundle2-exp=True
+  pushing to ssh://user@dummy/issue4455-dest
+  searching for changes
+  no changes found
+  remote: pushkey-abort: prepushkey hook exited with status 1
+  exporting bookmark @ failed!
+  [1]
+  $ hg -R ../issue4455-dest/ bookmarks
+  no bookmarks set
+
+  $ hg push -B @ ssh --config experimental.bundle2-exp=False
   pushing to ssh://user@dummy/issue4455-dest
   searching for changes
   no changes found
@@ -718,7 +728,7 b' Using ssh'
 Using http
 ----------
 
-  $ hg push -B @ http
+  $ hg push -B @ http --config experimental.bundle2-exp=True
   pushing to http://localhost:$HGPORT/
   searching for changes
   no changes found
@@ -727,3 +737,13 b' Using http'
   [1]
   $ hg -R ../issue4455-dest/ bookmarks
   no bookmarks set
+
+  $ hg push -B @ http --config experimental.bundle2-exp=False
+  pushing to http://localhost:$HGPORT/
+  searching for changes
+  no changes found
+  remote: pushkey-abort: prepushkey hook exited with status 1
+  exporting bookmark @ failed!
+  [1]
+  $ hg -R ../issue4455-dest/ bookmarks
+  no bookmarks set