github actions: Tweak if: condition syntax

.github/workflows/test.yml

@@ -55,7 +55,7 @@ jobs:
           pip install flake8 pytest pytest-cov coverage toml pint
           if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
       - name: Install coverage-lcov
-        if: "! inputs.skip-coverage"
+        if: ${{ !inputs.skip-coverage }}
         run: |
           pip install coverage-lcov
       - name: Lint with flake8
@@ -65,16 +65,16 @@ jobs:
           # exit-zero treats all errors as warnings.
           flake8 .  --count --exit-zero --max-complexity=10 --statistics
       - name: Test with py.test (with coverage)
-        if: "! inputs.skip-coverage"
+        if: ${{ !inputs.skip-coverage }}
         run: |
           coverage run -m pytest
           coverage-lcov
       - name: Test with py.test (without lcov coverage)
-        if: "inputs.skip-coverage"
+        if: ${{ inputs.skip-coverage }}
         run: |
           python -m pytest --cov=aioax25 --cov-report=term-missing
       - name: Coveralls
-        if: "! inputs.skip-coverage"
+        if: ${{ !inputs.skip-coverage }}
         uses: coverallsapp/github-action@master
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}