Increase diffusers example-test timeout to 60 minutes (#2591)

### What does this PR do?

Type of change: Bug fix

The diffusers example job can exhaust its 45-minute job budget while
tests are still progressing. On the same commit, an [initial attempt
timed
out](https://github.com/NVIDIA/Model-Optimizer/actions/runs/36456149060/job/109049102711),
while a [retry passed all 47 tests in
44m50s](https://github.com/NVIDIA/Model-Optimizer/actions/runs/36456149060/job/109115221419),
leaving only 10 seconds of headroom.

Increase the diffusers timeout to 60 minutes in
`.github/workflows/example_tests.yml` to accommodate the workload and
observed runtime variation. The other ONNX matrix entries retain their
45-minute timeout. This applies to both PR and nightly diffusers jobs.

### Usage

N/A — CI configuration change.

### Testing

- `pre-commit run --files .github/workflows/example_tests.yml` — passed
all applicable hooks.
- Parsed the caller and reusable workflow with `yaml.safe_load` and
inspected the timeout input and consumer.
- `git diff --check` — passed; reviewed the one-line diff.
- GPU tests were not rerun locally. CI validation of the increased
timeout is pending.

### Before your PR is "*Ready for review*"

Make sure you read and follow [Contributor
guidelines](https://github.com/NVIDIA/Model-Optimizer/blob/main/CONTRIBUTING.md)
and your commits are signed (`git commit -s -S`).

Make sure you read and follow the [Security Best
Practices](https://github.com/NVIDIA/Model-Optimizer/blob/main/SECURITY.md#security-coding-practices-for-contributors)
(e.g. avoiding hardcoded `trust_remote_code=True`, `torch.load(...,
weights_only=False)`, `pickle`, etc.).

- Is this change backward compatible?: ✅
- If you copied code from any other sources or added a new PIP
dependency, did you follow guidance in `CONTRIBUTING.md`: N/A — no
copied code or new dependencies.
- Did you write any new necessary tests?: N/A — one-line CI
configuration change; validation described above.
- Did you update
[Changelog](https://github.com/NVIDIA/Model-Optimizer/blob/main/CHANGELOG.rst)?:
N/A — CI-only change.
- Did you get Claude approval on this PR?: ❌ Not run; opening as a
draft.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated automated checks to allow ONNX example tests up to 60 minutes.
Other example tests retain their existing 45-minute limit. This change
affects test execution time limits only; it does not change application
features or behavior.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: ajrasane <131806219+ajrasane@users.noreply.github.com>

.github/workflows/example_tests.yml

@@ -179,7 +179,7 @@ jobs:
       # a torch-tensorrt build for the newer TensorRT is available.
       docker_image: "nvcr.io/nvidia/tensorrt:26.05-py3"
       example: ${{ matrix.example }}
-      timeout_minutes: 45
+      timeout_minutes: ${{ matrix.example == 'diffusers' && 60 || 45 }}
       pip_install_extras: "[onnx,hf,dev-test]"
       runner: ${{ startsWith(github.ref, 'refs/heads/pull-request/') && 'linux-amd64-gpu-rtxpro6000-latest-1' || 'linux-amd64-gpu-rtxpro6000-latest-2' }}
       allow_failure: ${{ contains(format(',{0},', vars.ALLOW_FAILURE_EXAMPLE_TESTS), format(',{0},', matrix.example)) }}