tooltip-ca-edit: Simplify wording to align with others

tooltip-ca-edit: Simplify wording to align with others

Previous text:
    "You can edit this page. Please use the preview button before saving"

Faults:
* Too wordy
* Mentions part of the interface on the next screen unnecessarily
* Unlike every other tooltip, isn't an verb to match the tab

New text:
    "Edit this page"

Advantages
* Shorter and simpler
* Aligns with other tooltips in matching the tab
* Doesn't mention an interface artefact from the next page

Change-Id: I03b45f8516094f990e5823f6dacb3d1fd651f383