Fix documentation build. (#43)

Fix documentation build.
Apparently trying to find a NumPy that works with Python 3.7-3.11 is
challenging. See also: #38

Author: jesnie

.github/workflows/build_test_deploy.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-python@v4
         with:
-          python-version: "3.10"
+          python-version: "3.7"
       - run: curl -sSL https://install.python-poetry.org | python3 -
       - run: poetry install
       - run: poetry run task test
@@ -60,7 +60,7 @@ jobs:
           path: gh-pages
       - uses: actions/setup-python@v4
         with:
-          python-version: "3.11"
+          python-version: "3.7"
       - run: curl -sSL https://install.python-poetry.org | python3 -
       - run: poetry install
       - run: poetry run task docs
@@ -84,7 +84,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-python@v4
         with:
-          python-version: "3.11"
+          python-version: "3.7"
       - run: curl -sSL https://install.python-poetry.org | python3 -
       - run: poetry build
       - run: poetry publish -u __token__ -p ${{ secrets.CHECK_SHAPES_PYPI_TOKEN }}