MathUtils: Make UUID RFC compliant. (#23679)

* MathUtils: Make UUID RFC compliant.

* Update MathUtils.js

Co-authored-by: mrdoob <[email protected]>

src/math/MathUtils.js

@@ -24,8 +24,8 @@ function generateUUID() {
 			_lut[ d2 & 0x3f | 0x80 ] + _lut[ d2 >> 8 & 0xff ] + '-' + _lut[ d2 >> 16 & 0xff ] + _lut[ d2 >> 24 & 0xff ] +
 			_lut[ d3 & 0xff ] + _lut[ d3 >> 8 & 0xff ] + _lut[ d3 >> 16 & 0xff ] + _lut[ d3 >> 24 & 0xff ];
 
-	// .toUpperCase() here flattens concatenated strings to save heap memory space.
-	return uuid.toUpperCase();
+	// .toLowerCase() here flattens concatenated strings to save heap memory space.
+	return uuid.toLowerCase();
 
 }