CI: Update Flake8 (#1932)

* Update Flake8 to version 3.9.2.
* Update Python used for the job to 3.10.
* Remove unused name from the matrix.
* Fix version of Python. It is a string, not float.

.github/workflows/flake8.yml

@@ -6,7 +6,6 @@ on:
 
 jobs:
   flake8:
-    name: ${{ matrix.directory }}
     runs-on: ubuntu-20.04
 
     steps:
@@ -15,12 +14,12 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: "3.10"
 
       - name: Install
         run: |
           python -m pip install --upgrade pip
-          pip install flake8==3.8.4
+          pip install flake8==3.9.2
 
       - name: Run Flake8
         run: |