AK: Rename <AK/AKString.h> to <AK/String.h>

This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.

Let's just not support building that way, so String.h can have an
objectively nicer name. :^)

Libraries/LibHTML/CSS/Length.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 
 class Length {
 public:

Libraries/LibHTML/CSS/Selector.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 #include <AK/Vector.h>
 #include <LibHTML/CSS/Specificity.h>
 

Libraries/LibHTML/CSS/StyleDeclaration.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 #include <LibHTML/CSS/StyleValue.h>
 
 class StyleDeclaration : public RefCounted<StyleDeclaration> {

Libraries/LibHTML/CSS/StyleValue.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 #include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
 #include <AK/StringView.h>

Libraries/LibHTML/CSS/StyledNode.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 #include <AK/HashMap.h>
 #include <AK/NonnullRefPtr.h>
 #include <AK/Optional.h>

Libraries/LibHTML/DOM/Document.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 #include <AK/NonnullRefPtrVector.h>
 #include <AK/OwnPtr.h>
 #include <LibHTML/CSS/StyleResolver.h>

Libraries/LibHTML/DOM/Element.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <LibHTML/DOM/ParentNode.h>
-#include <AK/AKString.h>
+#include <AK/String.h>
 
 class Attribute {
 public:

Libraries/LibHTML/DOM/Text.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <AK/AKString.h>
+#include <AK/String.h>
 #include <LibHTML/DOM/Node.h>
 
 class Text final : public Node {