Drop unused override for deprecated method SkinVector::shouldPreloadLogo

The parent method was deprecated in MW 1.32 and this override has been unused
ever since.

Bug: T255474
Change-Id: I811f7b3a6dba0bb1eebf36ed52e363affc8511d2

includes/SkinVector.php

@@ -98,15 +98,6 @@ class SkinVector extends SkinTemplate {
 		return new VectorTemplate( $this->getConfig(), $tp, $this->isLegacy() );
 	}
 
-	/**
-	 * Whether the logo should be preloaded with an HTTP link header or not
-	 * @since 1.29
-	 * @return bool
-	 */
-	public function shouldPreloadLogo() {
-		return true;
-	}
-
 	/**
 	 * Whether or not the legacy version of the skin is being used.
 	 *