Use summary message on non Main namespace pages

Instead of "How did you improve the page" show "Summary" on non-article
pages, like talk pages, when save an edit.

Follow up: Ie27bbd10e51a89340f502fa4cd6d0f7ca4683c3c

Bug: 69488
Change-Id: I602b538c24ca2c7e4232c44be76bf5e1af71f3a2
Merge "Use summary message on non Main namespace pages"