Don't suppress error codes in lint job, properly activate conda (#120769)
Before:
```
2024-02-28T02:38:24.3757573Z + conda activate /opt/conda/envs/py_3.9
2024-02-28T02:38:24.3757872Z
2024-02-28T02:38:24.3758116Z CondaError: Run 'conda init' before 'conda activate'
```
Now, this would actually fail the job, and I also fix the bug.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120769
Approved by: https://github.com/albanD, https://github.com/janeyx99, https://github.com/malfet
