CMake: Rename serenity_* helper functions/macros to ladybird_*

Author: https://github.com/ayeteadoe
Commit: 25f5936dee
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5249
Reviewed-by: https://github.com/gmta ✅

Libraries/LibThreading/CMakeLists.txt

@@ -3,7 +3,7 @@ set(SOURCES
     Thread.cpp
 )
 
-serenity_lib(LibThreading threading)
+ladybird_lib(LibThreading threading)
 target_link_libraries(LibThreading PRIVATE LibCore)
 
 if (WIN32)