Make $wgEmailConfirmToEdit only affect edit actions.

Previously it would affect all actions that use Title::userCan.
This used to be less noticable, but recently was expanded to include
the 'read' action. This only affected the case where both
$wgBlockDisablesLogin and $wgEmailConfirmedToEdit were enabled.

I don't think anyone was relying on the old behaviour as it was
undocumented, and only affected obscure permissions (checked with
Title::userCan and not depending on "edit" rights)

Follow-up b675be2083

Bug: T143790
Change-Id: I4ad93ed78de4f1ed444f73df6dc26d405a67e553
(cherry picked from commit d561f646b9b8424bd79cfc14729a622a143d9f12)