Adjust 3.8 stubtest command in CI

Author: smheidrich

.github/workflows/test.yml

@@ -75,8 +75,14 @@ jobs:
       - name: Run Mypy stubtest
         # XXX doesn't work on Pypy due to some symtable issues...
         if: "!startsWith(matrix.python-version, 'pypy')"
-        run: |
-          stubtest --ignore-disjoint-bases --allowlist stubtest-allowlist json_stream_rs_tokenizer
+        run: >
+          stubtest
+          ${{
+            !startsWith(matrix.python-version, '3.8')
+              && '--ignore-disjoint-bases'
+              || ''
+          }}
+          --allowlist stubtest-allowlist json_stream_rs_tokenizer
       - name: Save Rust/Cargo cache
         uses: actions/cache/save@v4
         if: always()