ve.init.mw.ViewPageTarget: Use original label for replaced tab

To verify
* Save "MediaWiki:Edit" with "Edit page" (anything not "Edit")
* Set this.tabLayout = 'replace';
* Observe that the ve-edit tab is now "Edit" (msg: vector-view-edit)
  instead of "Edit page" (msg: edit)

Bug: 42117
Change-Id: I2e7dd85cd14049101e2d49751d37797d77bc7c9d