Centre wardrobe tab labels and name the skin for what it covers

The label nudge in the shared tab handler exists to clear the icon on the
talent window's tabs, where the native anchor sits tight against it and
grown text would collide. The wardrobe's category tabs carry no icon and
centre their label, so the same nudge pushed every one of them off to the
right. It's now applied only to tabs that actually have a visible icon.

The settings entry covers three windows, so it's named for all three:
Advancement/Vanity/Wardrobe. The keys behind it move with it -- the db
table is skins.collections, after Collections, the container the three
windows and the tab row all hang off, and talentScale becomes
advancementScale. Nothing here has been released, so there's no stored
setting to migrate.

Modules/TalentFrame.lua

@@ -648,7 +648,7 @@ local function SkinFrame(frame)
 		-- run again on every show rather than once at hook time. The isSkinned
 		-- / backdrop guards inside ElvUI's handlers make re-runs cheap.
 		frame:HookScript("OnShow", function(self)
-			Skin:ApplyWindowScale("talentScale")
+			Skin:ApplyWindowScale("advancementScale")
 	Skin:Title(_G[FRAME_NAME.."TitleText"])
 			SkinCloseButton(self)
 			SkinBottomBar()
@@ -659,7 +659,7 @@ local function SkinFrame(frame)
 		end)
 	end
 
-	Skin:ApplyWindowScale("talentScale")
+	Skin:ApplyWindowScale("advancementScale")
 	Skin:Title(_G[FRAME_NAME.."TitleText"])
 	SkinCloseButton(frame)
 	SkinBottomBar()