Everywhere: Use east const in more places

These changes are compatible with clang-format 16 and will be mandatory
when we eventually bump clang-format version. So, since there are no
real downsides, let's commit them now.

Userland/Shell/main.cpp

@@ -85,7 +85,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             }
             (void)shell->highlight(editor);
         };
-        editor->on_tab_complete = [&](const Line::Editor&) {
+        editor->on_tab_complete = [&](Line::Editor const&) {
             return shell->complete();
         };
         editor->on_paste = [&](Utf32View data, Line::Editor& editor) {