LibWeb/WebGL2: Implement deleteSync

Libraries/LibWeb/WebGL/WebGL2RenderingContextBase.idl

@@ -398,7 +398,7 @@ interface mixin WebGL2RenderingContextBase {
     // Sync objects
     WebGLSync? fenceSync(GLenum condition, GLbitfield flags);
     [FIXME] GLboolean isSync(WebGLSync? sync); // [WebGLHandlesContextLoss]
-    [FIXME] undefined deleteSync(WebGLSync? sync);
+    undefined deleteSync(WebGLSync? sync);
     GLenum clientWaitSync(WebGLSync sync, GLbitfield flags, GLuint64 timeout);
     [FIXME] undefined waitSync(WebGLSync sync, GLbitfield flags, GLint64 timeout);
     [FIXME] any getSyncParameter(WebGLSync sync, GLenum pname);