Simplify MUS_OGG regex

Author: xPaw

rules.ini

@@ -13,7 +13,7 @@ CFG = \.cfg$ ; idTech1
 DATA_WIN = (?:^|/)data\.win$ ; GameMaker
 HDLL = \.hdll$ ; Heaps
 METADATA_DAT = (?:^|/)metadata\.dat$ ; RAGE
-MUS_OGG = (?:^|/)mus\_[\w0-9]+\.ogg$
+MUS_OGG = (?:^|/)mus\_\w+\.ogg$
 OPTIONS_INI = (?:^|/)options\.ini$ ; GameMaker
 PCK = \.pck$ ; Used for detecting Godot
 PIXI_JS = (?:^|/)pixi\.js$