Clean up things that include script/standard.h

Remove standard.h from files that don't use anything in it, and include
it in files that do.

src/test/util/mining.cpp

@@ -11,7 +11,6 @@
 #include <node/context.h>
 #include <pow.h>
 #include <primitives/transaction.h>
-#include <script/standard.h>
 #include <test/util/script.h>
 #include <util/check.h>
 #include <validation.h>