Hard deprecate Collation::singleton() and ::factory()

Change-Id: Idb2ea8efb982f8a815b6f7d724de493c9e15483e

RELEASE-NOTES-1.38

@@ -167,6 +167,7 @@ because of Phabricator reports.
 * Message::content() was hard-deprecated.
 * The following methods from the ParserOutput class were hard deprecated:
    - ::hideNewSection() - use ::setHideNewSection()
+* Collation::singleton() and ::factory() were hard-deprecated.
 * …
 
 === Other changes in 1.38 ===

includes/collation/Collation.php

@@ -36,6 +36,7 @@ abstract class Collation {
 	 * @return Collation
 	 */
 	public static function singleton() {
+		wfDeprecated( __METHOD__, '1.37' );
 		if ( !self::$instance ) {
 			global $wgCategoryCollation;
 			self::$instance = self::factory( $wgCategoryCollation );
@@ -51,6 +52,7 @@ abstract class Collation {
 	 * @return Collation
 	 */
 	public static function factory( $collationName ) {
+		wfDeprecated( __METHOD__, '1.37' );
 		return MediaWikiServices::getInstance()->getCollationFactory()->makeCollation( $collationName );
 	}