Reduce misc includes all around

src/catch2/internal/catch_assertion_handler.hpp

@@ -11,14 +11,11 @@
 #include <catch2/catch_assertion_info.hpp>
 #include <catch2/internal/catch_decomposer.hpp>
 #include <catch2/interfaces/catch_interfaces_capture.hpp>
-#include <catch2/internal/catch_lazy_expr.hpp>
 
 #include <string>
 
 namespace Catch {
 
-    class IResultCapture;
-
     struct AssertionReaction {
         bool shouldDebugBreak = false;
         bool shouldThrow = false;