message: Remove border radius for document toggle button
diff: .graphiql-container .docExplorerShow,
  .graphiql-container .historyShow {
  background: linear-gradient(#f7f7f7, #e2e2e2);
  + border-radius: 0;
  border-bottom: 1px solid #d0d0d0;
  border-right: none;
  border-top: none;
  