Remove "global" option from [compiler/coordinate](https://mujoco.readthedocs.io/en/latest/XMLreference.html#compiler-coordinate) attribute.

Keeping this rarely-used setting complicates the compiler logic and is blocking future improvements. In order to convert older models which used this option, load and save them in MuJoCo 2.3.3 or older.

PiperOrigin-RevId: 521739137
Change-Id: If0cb40d5db4879a4db9318cc2be258a7923e6e85

src/xml/xml_native_reader.cc

@@ -863,7 +863,10 @@ void mjXReader::Compiler(XMLElement* section, mjCModel* mod) {
     mod->fitaabb = (n==1);
   }
   if (MapValue(section, "coordinate", &n, coordinate_map, 2)) {
-    mod->global = (n==1);
+    if (n==1) {
+      throw mjXError(section, "global coordinates no longer supported. To convert existing models, "
+                              "load and save them in MuJoCo 2.3.3 or older");
+    }
   }
   if (MapValue(section, "angle", &n, angle_map, 2)) {
     mod->degree = (n==1);