[Bug] Tests compilation fails

[Mallets]

Describe the bug

Tests compilation fails when targeting zenoh-pico:

Scanning dependencies of target warnings_zenohpico
[ 73%] Building CXX object tests/CMakeFiles/warnings_zenohpico.dir/build/warnings.cxx.o
In file included from /tmp/zenoh-cpp/include/zenohpico.hxx:28,
                 from /tmp/zenoh-cpp/include/zenoh.hxx:25,
                 from /tmp/zenoh-cpp/tests/build/warnings.cxx:26:
/tmp/zenoh-cpp/include/zenohcxx/impl.hxx:329:2: error: extra ‘;’ [-Werror=pedantic]
  329 | };
      |  ^
/tmp/zenoh-cpp/include/zenohcxx/impl.hxx:577:2: error: extra ‘;’ [-Werror=pedantic]
  577 | };
      |  ^
cc1plus: all warnings being treated as errors
make[3]: *** [tests/CMakeFiles/warnings_zenohpico.dir/build.make:63: tests/CMakeFiles/warnings_zenohpico.dir/build/warnings.cxx.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:307: tests/CMakeFiles/warnings_zenohpico.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:571: tests/CMakeFiles/tests.dir/rule] Error 2
make: *** [Makefile:340: tests] Error 2

I assume a similar fix should be done as in #79

To reproduce

1. Clone zenoh-cpp
2. Compile tests with cmake --build . --target tests

System info

Ubuntu 20.04.6 LTS
AMD Ryzen 7 5800X

[Mallets]

Fixed by #81