Do not force full bg brightness on beginner-only songs.

Docs/Changelog_sm5.txt

@@ -4,6 +4,11 @@ The StepMania 5 Changelog covers all post-sm-ssc changes. For a list of changes
 from StepMania 4 alpha 5 to sm-ssc v1.2.5, see Changelog_sm-ssc.txt.
 ________________________________________________________________________________
 
+2015/11/09
+----------
+* [Gameplay] BG Brightness is no longer forced to 100% on songs that only
+  have a beginner chart. [kyzentun]
+
 2015/11/08
 ----------
 * [ScreenSelectMusic] Using lua music files for the section music and similar

src/Background.cpp

@@ -939,9 +939,14 @@ void BrightnessOverlay::SetActualBrightness()
 
 	float fBaseBGBrightness = g_fBGBrightness;
 
+	// Revision:  Themes that implement a training mode should handle the
+	// brightness for it.  The engine should not force the brightness for
+	// anything. -Kyz
+	/*
 	// HACK: Always show training in full brightness
 	if( GAMESTATE->m_pCurSong && GAMESTATE->m_pCurSong->IsTutorial() )
 		fBaseBGBrightness = 1.0f;
+	*/
 
 	fLeftBrightness *= fBaseBGBrightness;
 	fRightBrightness *= fBaseBGBrightness;