Fix compilation error with gcc 11

[stac47]

Hello,
Fixing this compilation issue. gcc 11 does not accept this wrong constructor declaration anymore.

In file included from BUILD/jsoncons-0.157.2/include/jsoncons/basic_json.hpp:35,                                                                                                                                           from BUILD/jsoncons-0.157.2/include/jsoncons/json.hpp:10,
                 from BUILD/jsoncons-0.157.2/tests/src/JSONTestSuite_tests.cpp:13:
BUILD/jsoncons-0.157.2/include/jsoncons/json_reader.hpp:37:47: error: expected unqualified-id before 'const'
   37 |     json_utf8_to_other_visitor_adaptor<CharT>(const json_utf8_to_other_visitor_adaptor<CharT>&) = delete;
      |                                               ^~~~~
BUILD/jsoncons-0.157.2/include/jsoncons/json_reader.hpp:37:47: error: expected ')' before 'const'                                                                                                            37 |     json_utf8_to_other_visitor_adaptor<CharT>(const json_utf8_to_other_visitor_adaptor<CharT>&) = delete;
      |                                              ~^~~~~
      |                                               )

Regards,
Stac

[danielaparker]

Thanks!