[dynamo][dashboard] Clear local changes before pulling git repos (#96667)
Current dashboard issue is due to a .pt file in torchbench that has beeen modified for some reason. This clears any local changes before pulling.
Tested in a duplicate dashboard environment with the same .pt file modified:
* Before the change to this makefile, `make pull-deps` fails
* After the change to this makefile, `make pull-deps` succeeds.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96667
Approved by: https://github.com/anijain2305
