GH actions: Don't use Poetry >=v2

Poetry v2 drops support for Python v3.8 which we are still using.

.github/workflows/format.yaml

@@ -19,6 +19,8 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
       - uses: Gr1N/setup-poetry@v8
+        with:
+          poetry-version: "<2"
       - uses: actions/cache@v2
         with:
           path: ~/.cache/pypoetry/virtualenvs

.github/workflows/lint.yaml

@@ -20,6 +20,8 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Set up Poetry
         uses: Gr1N/setup-poetry@v8
+        with:
+          poetry-version: "<2"
       - uses: actions/cache@v2
         with:
           path: ~/.cache/pypoetry/virtualenvs

.github/workflows/publish.yaml

@@ -18,6 +18,8 @@ jobs:
       - uses: actions/setup-python@v4
       - name: Set up Poetry
         uses: Gr1N/setup-poetry@v8
+        with:
+          poetry-version: "<2"
       - name: Configure access
         run: |
           poetry config repositories.testpypi https://test.pypi.org/legacy/

.github/workflows/self_test.yaml

@@ -19,6 +19,8 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Set up Poetry
         uses: Gr1N/setup-poetry@v8
+        with:
+          poetry-version: "<2"
       - uses: actions/cache@v2
         with:
           path: |

.github/workflows/tests.yaml

@@ -20,6 +20,8 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Set up Poetry
         uses: Gr1N/setup-poetry@v8
+        with:
+          poetry-version: "<2"
       - uses: actions/cache@v2
         with:
           path: |