[tune](deps): Bump torch from 1.7.0 to 1.9.0 in /python/requirements

Bumps [torch](https://github.com/pytorch/pytorch) from 1.7.0 to 1.9.0.
- [Release notes](https://github.com/pytorch/pytorch/releases)
- [Changelog](https://github.com/pytorch/pytorch/blob/master/RELEASE.md)
- [Commits](pytorch/pytorch@v1.7.0...v1.9.0)

---
updated-dependencies:
- dependency-name: torch
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

python/requirements/ml/requirements_dl.txt

@@ -9,6 +9,6 @@ torchvision==0.10.0;sys_platform=="darwin"
 
 # On non-OSX machines only install CPU version of torch and torchvision
 -f https://download.pytorch.org/whl/torch_stable.html
-torch==1.9.0+cpu;sys_platform!="darwin"
+torch==1.9.1;sys_platform!="darwin"
 -f https://download.pytorch.org/whl/torch_stable.html
 torchvision==0.10.0+cpu;sys_platform!="darwin"