ci: use ZLIB_VERSION 1.3 for MAC OS tests

Author: ivanitskiy

.github/workflows/ci.yaml

@@ -75,6 +75,8 @@ jobs:
           restore-keys: nginx-
       - name: run tests
         uses: actions-rs/cargo@v1
+        env:
+          ZLIB_VERSION: "1.3"
         with:
           command: test
           args: --verbose