Remove Unnecessary Includes in Headers (#4275)

* refactor: remove unnecessary includes in headers

* fix: formatting

* chore: changelog

* fix: scrollbar

* fix: suggestions and old appbase remains

* fix: suggestion

* fix: missing Qt forward declarations

* fix: another qt include

* fix: includes for precompiled-headers=off

* Add missing `<memory>` includes

* Add missing `#pragma once`

* Fix tests

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/widgets/splits/ClosedSplits.hpp

@@ -1,8 +1,6 @@
 #pragma once
 
-#include "common/Channel.hpp"
-#include "widgets/helper/NotebookTab.hpp"
-
+#include <QList>
 #include <QUuid>
 
 #include <deque>
@@ -11,6 +9,8 @@
 
 namespace chatterino {
 
+class NotebookTab;
+
 class ClosedSplits
 {
 public: