Everywhere: Refer to dlfcn*.h by its non-prefixed name

Author: https://github.com/timschumi
Commit: 27bfb81702
Pull-request: https://github.com/SerenityOS/serenity/pull/14854

Userland/Libraries/LibC/dlfcn.cpp

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibDl/dlfcn_integration.h>
+#include <dlfcn_integration.h>
 
 // These are used by libdl and are filled in by the dynamic loader.
 DlCloseFunction __dlclose;