Remove getdir from mjpResourceProvider.

All known implementations were effectively the same as the default fallback. It was just adding unneeded complexity. Removing this now will help with upcoming improvements to resource providers.

PiperOrigin-RevId: 855163273
Change-Id: I529fc18d0d03a8dc676c909ec9e4b1da1454d414

src/engine/engine_plugin.cc

@@ -252,7 +252,6 @@ bool GlobalTable<mjpResourceProvider>::ObjectEqual(const mjpResourceProvider& p1
           p1.open == p2.open &&
           p1.read == p2.read &&
           p1.close == p2.close &&
-          p1.getdir == p2.getdir &&
           p1.modified == p2.modified &&
           p1.data == p2.data);
 }