Cleanup includes in sources

Mainly just removes some unused includes, but sometimes the include
is replaced by a smaller header instead.

src/catch2/internal/catch_assertion_handler.cpp

@@ -8,10 +8,8 @@
 #include <catch2/internal/catch_assertion_handler.hpp>
 #include <catch2/interfaces/catch_interfaces_config.hpp>
 #include <catch2/internal/catch_context.hpp>
-#include <catch2/internal/catch_enforce.hpp>
 #include <catch2/internal/catch_debugger.hpp>
 #include <catch2/internal/catch_test_failure_exception.hpp>
-#include <catch2/interfaces/catch_interfaces_registry_hub.hpp>
 #include <catch2/matchers/catch_matchers_string.hpp>
 
 namespace Catch {