Remove needless move() calls in cloud_print/gcp20

After https://codereview.chromium.org/1553493002/, the compiler can
inform us that these are not needed and in fact harmful:

..\..\cloud_print\gcp20\prototype\privet_http_server.cc(418,10) :  error: moving a local object in a return statement prevents copy elision [-Werror,-Wpessimizing-move]
  return std::move(response);
         ^
..\..\cloud_print\gcp20\prototype\privet_http_server.cc(418,10) :  note: remove std::move call here
  return std::move(response);
         ^~~~~~~~~~

..\..\cloud_print\gcp20\prototype\cloud_print_url_request_context_getter.cc(30,16) :  error: moving a temporary object prevents copy elision [-Werror,-Wpessimizing-move]
    context_ = std::move(builder.Build());
               ^
..\..\cloud_print\gcp20\prototype\cloud_print_url_request_context_getter.cc(30,16) :  note: remove std::move call here
    context_ = std::move(builder.Build());
               ^~~~~~~~~~               ~

BUG=82385
TBR=vitalybuka

Review URL: https://codereview.chromium.org/1552613003 .

Cr-Commit-Position: refs/heads/master@{#367067}
3 files changed