Update gluonts.shell requirements (#3233)

*Issue #, if available:* 
- https://github.com/awslabs/gluonts/security/dependabot/31
- https://github.com/awslabs/gluonts/security/dependabot/32

*Description of changes:*
- Update waitress to the minimum recommended version as per the above
issues
- Update flask to the latest release
- Enable gluonts.shell tests in the PyTorch tests workflow


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**Please tag this pr with at least one of these labels to make our
release process faster:** BREAKING, new feature, bug fix, other change,
dev setup

.github/workflows/tests-torch.yml

@@ -21,10 +21,9 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
-        pip install ".[arrow]" \
+        pip install ".[arrow,torch,shell]" \
           -r requirements/requirements-test.txt \
-          -r requirements/requirements-extras-m-competitions.txt \
-          -r requirements/requirements-pytorch.txt
+          -r requirements/requirements-extras-m-competitions.txt
         pip install --no-deps -r requirements/requirements-extras-cpflows.txt
     - name: Test with pytest
       run: |

requirements/requirements-extras-shell.txt

@@ -1,2 +1,2 @@
-flask~=2.0
-waitress~=2.1.2
+flask~=3.0
+waitress~=3.0.1