Clean up (#27983)

examples/jsm/lines/LineMaterial.js

@@ -603,12 +603,10 @@ class LineMaterial extends ShaderMaterial {
 		if ( value === true ) {
 
 			this.defines.USE_ALPHA_TO_COVERAGE = '';
-			this.extensions.derivatives = true;
 
 		} else {
 
 			delete this.defines.USE_ALPHA_TO_COVERAGE;
-			this.extensions.derivatives = false;
 
 		}
 

examples/webgl_materials_channels.html

@@ -199,7 +199,6 @@
 				materialVelocity.uniforms.displacementMap.value = displacementMap;
 				materialVelocity.uniforms.displacementScale.value = SCALE;
 				materialVelocity.uniforms.displacementBias.value = BIAS;
-				materialVelocity.extensions.derivatives = true;
 
 				//