Bump torchvision from 0.12.0 to 0.20.0 in /demo-notebooks/guided-demos

Bumps [torchvision](https://github.com/pytorch/vision) from 0.12.0 to 0.20.0.
- [Release notes](https://github.com/pytorch/vision/releases)
- [Commits](pytorch/vision@v0.12.0...v0.20.0)

---
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==1.9.5
 ray_lightning
 torchmetrics==0.9.1
-torchvision==0.12.0
+torchvision==0.20.0

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

@@ -1,4 +1,4 @@
 pytorch_lightning==1.9.5
 ray_lightning
 torchmetrics==0.9.1
-torchvision==0.12.0
+torchvision==0.20.0

demo-notebooks/guided-demos/requirements.txt

@@ -1,4 +1,4 @@
 pytorch_lightning==2.2.5
 ray_lightning
 torchmetrics==1.4.0
-torchvision==0.18.0
+torchvision==0.20.0