Remove clamp macro

Doesn't really need to exist since  all it's doing is inlining std::clamp.

src/CombinedLifeMeterTug.cpp

@@ -126,7 +126,7 @@ void CombinedLifeMeterTug::ChangeLife( PlayerNumber pn, float fPercentToMove )
 		}
 
 		/* Clamp the life meter only for calculating the multiplier. */
-		fLifePercentage = clamp( fLifePercentage, 0.0f, 1.0f );
+		fLifePercentage = std::clamp( fLifePercentage, 0.0f, 1.0f );
 		fPercentToMove *= SCALE( fLifePercentage, 0.f, 1.f, 0.2f, 1.f);
 	}