NSGL: ANGLE exists

(cherry picked from commit 8f2f766f0d2ed476c03a2ae02e48ac41a9602b03)
diff --git a/src/nsgl_context.m b/src/nsgl_context.m
index e984cae..e581b6f 100644
--- a/src/nsgl_context.m
+++ b/src/nsgl_context.m
@@ -161,7 +161,7 @@
     if (ctxconfig->client == GLFW_OPENGL_ES_API)
     {
         _glfwInputError(GLFW_API_UNAVAILABLE,
-                        "NSGL: OpenGL ES is not available on macOS");
+                        "NSGL: OpenGL ES is not available via NSGL");
         return GLFW_FALSE;
     }