core/CMakeLists: Make all web_service-related libraries private

Now that all external dependencies are hidden, we can remove
json-headers from the publically linked libraries, as the use of this
library is now completely hidden from external users of the web_service
library. We can also make the web_services library private as well,
considering it's not a requirement. If a library needs to link in
web_service, it should be done explicitly -- not via indirect linking.

src/core/CMakeLists.txt

@@ -398,7 +398,7 @@ target_link_libraries(core PUBLIC common PRIVATE audio_core video_core)
 target_link_libraries(core PUBLIC Boost::boost PRIVATE fmt lz4_static mbedtls opus unicorn open_source_archives)
 if (ENABLE_WEB_SERVICE)
     target_compile_definitions(core PRIVATE -DENABLE_WEB_SERVICE)
-    target_link_libraries(core PUBLIC json-headers web_service)
+    target_link_libraries(core PRIVATE web_service)
 endif()
 
 if (ARCHITECTURE_x86_64)