Update build-simpleplugin.yml (#4)

Co-authored-by: Qv2ray-dev <59914293+Qv2ray-dev@users.noreply.github.com>

Author: ymshenyu

.github/workflows/build-simpleplugin.yml

@@ -113,8 +113,8 @@ jobs:
         if: matrix.platform == 'ubuntu-16.04'
         shell: bash
         env:
-          CC: /usr/bin/gcc-9
-          CXX: /usr/bin/g++-9
+          CC: /usr/bin/gcc-7
+          CXX: /usr/bin/g++-7
           CXXFLAGS: -fno-sized-deallocation
         run: |
           mkdir build