[iwyu] Minor iwyu fixes.

src/ast/modules.h

Index: src/ast/modules.h
diff --git a/src/ast/modules.h b/src/ast/modules.h
index 94550fb5c99b439a89855b565555e773ab228246..ce8aba8d709cd2a2867c39129206ef6c0180ec03 100644
--- a/src/ast/modules.h
+++ b/src/ast/modules.h
@@ -6,7 +6,6 @@
 #define V8_AST_MODULES_H_
 
 #include "src/parsing/scanner.h"  // Only for Scanner::Location.
-#include "src/pending-compilation-error-handler.h"
 #include "src/zone/zone-containers.h"
 
 namespace v8 {
@@ -16,6 +15,7 @@ namespace internal {
 class AstRawString;
 class ModuleInfo;
 class ModuleInfoEntry;
+class PendingCompilationErrorHandler;
 
 class ModuleDescriptor : public ZoneObject {
  public: