[ci] Install lua-cjson2 during test task

Author: tobil4sk

.github/workflows/ci.yml

@@ -17,7 +17,6 @@ jobs:
         run: |
           pip install hererocks
           hererocks lua_install -r^ --${{ matrix.lua }}
-          luarocks install lua-cjson2
         env:
           MACOSX_DEPLOYMENT_TARGET: 11.0
       - name: Build lua-simdjson
@@ -27,5 +26,6 @@ jobs:
       - name: Run tests
         run: |
           source lua_install/bin/activate
+          luarocks install lua-cjson2
           luarocks install busted
           busted --verbose