shelve: lowercase flag description

The help for --unknown is the *only* command that started with a capital letter

hgext/shelve.py

@@ -766,7 +766,7 b' def _dounshelve(ui, repo, *shelved, **op'
          [('A', 'addremove', None,
            _('mark new/missing files as added/removed before shelving')),
           ('u', 'unknown', None,
-           _('Store unknown files in the shelve')),
+           _('store unknown files in the shelve')),
           ('', 'cleanup', None,
            _('delete all shelved changes')),
           ('', 'date', '',

tests/test-shelve.t

@@ -54,7 +54,7 b' shelve has a help message'
   
    -A --addremove           mark new/missing files as added/removed before
                             shelving
-   -u --unknown             Store unknown files in the shelve
+   -u --unknown             store unknown files in the shelve
       --cleanup             delete all shelved changes
       --date DATE           shelve with the specified commit date
    -d --delete              delete the named shelved change(s)