Disables rate limit for headless rendering app (#3089)

# Description

For some simple cases, disabling rate limit in the runloop can help
improve performance for rendering.
Nevertheless, we should not need to enable rate limit in headless cases.

## Type of change

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- Bug fix (non-breaking change which fixes an issue)
- New feature (non-breaking change which adds functionality)


## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./isaaclab.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [ ] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

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Co-authored-by: ooctipus <zhengyuz@nvidia.com>

apps/isaaclab.python.headless.rendering.kit

@@ -88,6 +88,9 @@ app.audio.enabled = false
 # Enable Vulkan - avoids torch+cu12 error on windows
 app.vulkan = true
 
+# Disables rate limit in runloop
+app.runLoops.main.rateLimitEnabled=false
+
 # disable replicator orchestrator for better runtime perf
 exts."omni.replicator.core".Orchestrator.enabled = false