Replace "coll-add_this_page" by "coll-add_page_tooltip"

The message "coll-add_this_page" is for a link text.
The tooltip for the link is "coll-add_page_tooltip".

Change-Id: I9c7188be7f9b94ddf1e43f33001eb459665d4280
Merge "Replace "coll-add_this_page" by "coll-add_page_tooltip""