requirements: move the comment about manifestv2 in the module

This is about requirements, so lets put it into the requirements module.

We are about to remove code it was previously attached too.

Differential Revision: https://phab.mercurial-scm.org/D12033

mercurial/localrepo.py

@@ -1274,11 +1274,6 b' class localrepository(object):'
     used.
     """
 
-    # obsolete experimental requirements:
-    #  - manifestv2: An experimental new manifest format that allowed
-    #    for stem compression of long paths. Experiment ended up not
-    #    being successful (repository sizes went up due to worse delta
-    #    chains), and the code was deleted in 4.6.
     supportedformats = {
         requirementsmod.REVLOGV1_REQUIREMENT,
         requirementsmod.GENERALDELTA_REQUIREMENT,

mercurial/requirements.py

@@ -7,6 +7,12 b''
 
 from __future__ import absolute_import
 
+# obsolete experimental requirements:
+#  - manifestv2: An experimental new manifest format that allowed
+#    for stem compression of long paths. Experiment ended up not
+#    being successful (repository sizes went up due to worse delta
+#    chains), and the code was deleted in 4.6.
+
 GENERALDELTA_REQUIREMENT = b'generaldelta'
 DOTENCODE_REQUIREMENT = b'dotencode'
 STORE_REQUIREMENT = b'store'