Set TEST_GXPDF=1 only for Python 3.11

Author: utensil

.github/workflows/ci.yml

@@ -14,7 +14,6 @@ concurrency:
 env:
   PYTHONUNBUFFERED: "1"
   FORCE_COLOR: "1"
-  TEST_GXPDF: "1"
 
 jobs:
   build:
@@ -59,6 +58,10 @@ jobs:
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
         biber-version: "latest"
+    - name: Set environment variables
+      if: "matrix.python-version == '3.11'"
+      run: |
+        echo "TEST_GXPDF=1" >> "$GITHUB_ENV"
     - name: Test
       run: |
         PYTEST_ARGS=();