Avoid requiring TBB when not building io_usd (#845)

Summary:
TBB is a transitive dependency of USD, so it should not be required when USD is not being built. This issue was mistakenly not fixed by #843.

## Checklist:

- [x] Adheres to the [style guidelines](https://facebookresearch.github.io/momentum/docs/developer_guide/style_guide)
- [x] Codebase formatted by running `pixi run lint`

Pull Request resolved: #845

Test Plan:
```
pixi run  test
```

Reviewed By: fbogo

Differential Revision: D87385804

Pulled By: jeongseok-meta

fbshipit-source-id: a547b96272b568e78293fe86d6b2cd3960eb4fc9

Author: jeongseok-meta

CMakeLists.txt

@@ -120,10 +120,10 @@ find_package(nlohmann_json CONFIG REQUIRED)
 find_package(openfbx CONFIG REQUIRED)
 if(MOMENTUM_BUILD_IO_USD)
   find_package(pxr CONFIG REQUIRED HINTS ${CMAKE_INSTALL_PREFIX} ${CMAKE_INSTALL_PREFIX}/cmake)
+  find_package(TBB CONFIG REQUIRED)
 endif()
 find_package(re2 MODULE REQUIRED)
 find_package(spdlog CONFIG REQUIRED)
-find_package(TBB CONFIG REQUIRED)
 find_package(urdfdom CONFIG REQUIRED)
 
 if(MOMENTUM_BUILD_RENDERER)