Downgrade python-version in job running Slither to 3.10.0

In a previous commit we wre trying to upgrade Python version to `3.11.0`, but we
discovered that the Slither installation does currently not work correctly when
that version is used (there's an Issue created for that, see
crytic/slither#1466). One of the recommended solutions
is temporary downgrade to Python `3.10`.

.github/workflows/contracts-ecdsa.yml

@@ -102,7 +102,7 @@ jobs:
 
       - uses: actions/setup-python@v4
         with:
-          python-version: 3.11.0
+          python-version: 3.10.0
 
       - name: Install Solidity
         env:

.github/workflows/contracts-random-beacon.yml

@@ -102,7 +102,7 @@ jobs:
 
       - uses: actions/setup-python@v4
         with:
-          python-version: 3.11.0
+          python-version: 3.10.0
 
       - name: Install Solidity
         env: