Remove AFPData::dup

The method, which simply duplicates an AFPData instance, is only used
when casting types, to return a different instance when the object
already has the desired type.
However, nothing is assuming that, so we can just return the original
instance and save some time.

Bug: T234427
Change-Id: Id8067b418a00260ceead35f234e55268390699ab

includes/parser/AFPData.php

@@ -98,13 +98,6 @@ class AFPData {
 		}
 	}
 
-	/**
-	 * @return AFPData
-	 */
-	private function dup() {
-		return new AFPData( $this->type, $this->data );
-	}
-
 	/**
 	 * @param AFPData $orig
 	 * @param string $target
@@ -112,7 +105,7 @@ class AFPData {
 	 */
 	public static function castTypes( AFPData $orig, $target ) {
 		if ( $orig->type === $target ) {
-			return $orig->dup();
+			return $orig;
 		}
 		if ( $orig->type === self::DUNDEFINED ) {
 			// This case should be handled at a higher level, to avoid implicitly relying on what