CMakeLists: Disable YUZU_ENABLE_BOXCAT if ENABLE_WEB_SERVICE is disabled

Boxcat is a web service but is still enabled if ENABLE_WEB_SERVICE is
disabled during the CMake stage, which causes compilation issues with
either missing headers or missing libraries.

This disables YUZU_ENABLE_BOXCAT regardless of the input if
ENABLE_WEB_SERVICE is disabled.