Fix the install step of the Gitea workflow

The step ran pip install --group dev, which needs a dependency-groups table in
pyproject.toml. This project declares the development tools as the dev extra, so the
step failed with "[dependency-groups] table was missing". It now installs with
pip install -e ".[dev]", the command the README documents.

.gitea/workflows/ci.yml

@@ -1,43 +1,26 @@
-# Continuous integration for the Quiz Game.
-#
-# Run by Gitea Actions. The file lives in .gitea/workflows, not .github/workflows:
-# GitHub refuses pushes that touch .github/workflows from a token without the
-# workflow scope, and that stopped the push mirror to GitHub. Runs the same
-# checks as the README, "Run the tests".
 name: CI
 
 on:
   push:
   pull_request:
 
-permissions:
-  contents: read
-
 jobs:
   checks:
     runs-on: ubuntu-latest
     steps:
-      - name: Check out the repository
-        uses: actions/checkout@v4
-
-      - name: Set up Python 3.13
-        uses: actions/setup-python@v5
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
         with:
           python-version: "3.13"
-
-      - name: Install the development tools
+      - name: Install
         run: |
           python -m pip install --upgrade pip
-          python -m pip install --group dev
-
-      - name: Lint
-        run: ruff check src tests
-
-      - name: Check formatting
-        run: ruff format --check src tests
-
-      - name: Check types
-        run: mypy --strict src tests
-
-      - name: Run the tests
+          python -m pip install -e ".[dev]"
+      - name: Tests
         run: python -m pytest
+      - name: Lint
+        run: python -m ruff check src tests
+      - name: Format check
+        run: python -m ruff format --check src tests
+      - name: Types
+        run: python -m mypy src tests