[BE] Make `test_no_triton_on_import` simple (#102674)
Do not try to parse raised exception for no good reason
Add short description
Reduce script to a single line
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### <samp>🤖 Generated by Copilot at ea4164e</samp>
> _`test_no_triton_on_import`_
> _Cleans up the code, adds docs_
> _No hidden errors_
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102674
Approved by: https://github.com/cpuhrsch, https://github.com/albanD
