[dynamo][dashboard] fix triton clone step in dashboard (#96623)
previously this would clone triton, and then try to checkout without being in the git repo directory. This wasn't usually a problem because the environment already had a triton repo downloaded; but I ran into this while trying to construct a new environment.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96623
Approved by: https://github.com/anijain2305
