Everywhere: Remove unnecessary headers 1/4

Arbitrarily split up to make git bisect easier.

These unnecessary #include's were found by combining an automated tool (which
determined likely candidates) and some brain power (which decided whether
the #include is also semantically superfluous).

My favorite #include:

    #include "Applications/Piano/Music.h" // You can't have too much music in life!

AK/Format.cpp

@@ -35,7 +35,6 @@
 #    include <Kernel/Thread.h>
 #else
 #    include <stdio.h>
-#    include <unistd.h>
 #endif
 
 namespace AK {