[BUGFIX] Made changeDiff not use the suffixed difficulty as the cur…

…rent difficulty on freeplay

In the `changeDiff` method of `FreeplayState`, when the current song isn't "Random", `rememberedDifficulty` gets assigned to the suffixed version of  `currentDifficulty` instead of `currentDifficulty` itself. Later, when `generateSongList` gets called, `currentDifficulty` gets assigned to `rememberedDifficulty`, which means `currentDifficulty` changed to its suffixed version.

Because difficulty selection in freeplay doesn't use the suffixed versions of the difficulties, adding the suffix creates some bugs. From my testing (which I recorded a video of), I found that the bugs prevent freeplay from selecting custom difficulties on variations other than "default" and "erect".

source/funkin/ui/freeplay/FreeplayState.hx

@@ -1785,14 +1785,13 @@ class FreeplayState extends MusicBeatSubState
       var songScore:Null<SaveScoreData> = Save.instance.getSongScore(daSong.songId, suffixedDifficulty);
       intendedScore = songScore?.score ?? 0;
       intendedCompletion = songScore == null ? 0.0 : ((songScore.tallies.sick + songScore.tallies.good) / songScore.tallies.totalNotes);
-      rememberedDifficulty = suffixedDifficulty;
     }
     else
     {
       intendedScore = 0;
       intendedCompletion = 0.0;
-      rememberedDifficulty = currentDifficulty;
     }
+    rememberedDifficulty = currentDifficulty;
 
     if (intendedCompletion == Math.POSITIVE_INFINITY || intendedCompletion == Math.NEGATIVE_INFINITY || Math.isNaN(intendedCompletion))
     {