build(deps): bump torchvision in /demo-notebooks/guided-demos

Bumps [torchvision](https://github.com/pytorch/vision) from 0.20.1 to 0.21.0.
- [Release notes](https://github.com/pytorch/vision/releases)
- [Commits](pytorch/vision@v0.20.1...v0.21.0)

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

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

Author: dependabot[bot]

demo-notebooks/guided-demos/notebook-ex-outputs/requirements.txt

@@ -1,4 +1,4 @@
 pytorch_lightning==2.4.0
 ray_lightning
 torchmetrics==1.6.0
-torchvision==0.20.1
+torchvision==0.21.0

demo-notebooks/guided-demos/preview_nbs/requirements.txt

@@ -1,4 +1,4 @@
 pytorch_lightning==2.4.0
 ray_lightning
 torchmetrics==1.6.0
-torchvision==0.20.1
+torchvision==0.21.0

demo-notebooks/guided-demos/requirements.txt

@@ -1,4 +1,4 @@
 pytorch_lightning==2.4.0
 ray_lightning
 torchmetrics==1.6.0
-torchvision==0.20.1
+torchvision==0.21.0