remove VERIFY_SETUP define

This define was seemingly introduced for VERIFY mode code with side
effects (for setup purposes), that should just be executed without any
checks. The same can be achieved by putting it in an `#if VERIFY` block,
so we can remove it.

src/util.h

@@ -135,10 +135,8 @@ static const secp256k1_callback default_error_callback = {
 /* Like assert(), but when VERIFY is defined. */
 #if defined(VERIFY)
 #define VERIFY_CHECK CHECK
-#define VERIFY_SETUP(stmt) do { stmt; } while(0)
 #else
 #define VERIFY_CHECK(cond)
-#define VERIFY_SETUP(stmt)
 #endif
 
 static SECP256K1_INLINE void *checked_malloc(const secp256k1_callback* cb, size_t size) {