Drop the aarch64-only usd-exchange override

Develop isaac-sim#6938 re-imposed the platform split by overriding usd-exchange
to aarch64, so x86_64 would keep usd-core. This branch removes usd-core
entirely, and the merge kept that override -- so the kit-less image
installed no pxr at all and every converter test failed with
"No module named 'pxr'". The install CLI applies these overrides too,
not just uv sync, so the effect reached both paths.

Author: hujc7

pyproject.toml

@@ -426,10 +426,6 @@ override-dependencies = [
     # ovphysx caps packaging at <24 and isaacsim-core pins ==26.0; both caps are
     # stricter than the code needs, so widening lets them resolve together at 26.0.
     "packaging>=20,<27",
-    # usd-exchange and usd-core each vendor a full ``pxr`` built against a different
-    # USD version, and newton[importers] pulls usd-exchange unmarked. Re-impose the
-    # platform split from [project.dependencies] so only one lands per platform.
-    "usd-exchange>=2.2 ; platform_machine == 'aarch64'",
 ]
 # ``ov`` stays forked: it pulls ovrtx, which is not validated alongside Isaac Sim.
 # ``teleop`` bundles isaacsim, so it inherits that pair.