fix: Specify Python version in the integration tests (#3340)

Fixes old Python on Mac OS and Windows.

.github/workflows/integration-tests-reusable.yml

@@ -43,7 +43,7 @@ jobs:
  run: echo "target-runtime-version=[\"oldest\"]" >> $GITHUB_OUTPUT
  - name: Populate shard list
  id: populate-shard-list
- run: echo "shard-list=[" $(seq -s , 1 ${{ inputs.num_shards }}) "]" >> $GITHUB_OUTPUT
+ run: echo "shard-list=[`seq -s , 1 ${{ inputs.num_shards }}`]" >> $GITHUB_OUTPUT
  outputs:
  os-list: ${{ steps.populate-os-list-all.outputs.os-list }} ${{ steps.populate-os-list-one.outputs.os-list }}
  os-mapping: ${{ steps.populate-os-mapping.outputs.os-mapping }}
@@ -90,6 +90,10 @@ jobs:
  run: pip install lit OutputCheck pyyaml
  - uses: actions/setup-node@v3
  - run: npm install bignumber.js
+ - name: Set up Python
+ uses: actions/setup-python@v4
+ with: 
+ python-version: '3.11'
  - name: Checkout Dafny
  uses: actions/checkout@v3
  with: