Simplify test workflow by removing lpeg modifications

Removed sed commands for lpeg replacement in tests.

Author: olegrok

.github/workflows/test_on_push.yaml

@@ -35,8 +35,6 @@ jobs:
       - name: Run tests
         run: |
           git clone https://github.com/bjornbytes/graphql-lua
-          sed -i 's/lpeg/lulpeg/g' graphql-lua/graphql-0.0.2-1.rockspec
-          sed -i "s/local lpeg = require 'lpeg'/local lpeg = require 'lulpeg'/g" graphql-lua/graphql/parse.lua
           tt rocks make --chdir graphql-lua
           tt rocks install luatest 1.2.1
           .rocks/bin/luatest -v