fix: disabling Physics2D or Physics compilation errors (#3422)

This PR resolves the issue where disabling the physics or physics2d
package module while leaving the other still enabled could cause
compilation issues.

## Changelog

- Fixed: Issue where disabling the physics or physics2D package modules
could result in a compilation error.

## Testing and Documentation

- No tests have been added. (has to be manually tested)
- No documentation changes or additions were necessary.

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## Backport
No backport is needed since this is a v2.x specific issue.
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Author: NoelStephensUnity

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -18,6 +18,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Fixed inconsistencies in the `OnSceneEvent` callback. (#3458)
 - Fixed issues with the `NetworkBehaviour` and `NetworkVariable` length safety checks. (#3405)
 - Fixed memory leaks when domain reload is disabled. (#3427)
+- Fixed issue where disabling the physics or physics2D package modules could result in a compilation error. (#3422)
 - Fixed an exception being thrown when unregistering a custom message handler from within the registered callback. (#3417)
 
 ### Changed