crypto/secp256k1: remove useless code (#17728)

`(void)data;` may cause link error on Windows.

crypto/secp256k1/libsecp256k1/src/secp256k1.c

@@ -26,7 +26,6 @@
 } while(0)
 
 static void default_illegal_callback_fn(const char* str, void* data) {
-    (void)data;
     fprintf(stderr, "[libsecp256k1] illegal argument: %s\n", str);
     abort();
 }
@@ -37,7 +36,6 @@ static const secp256k1_callback default_illegal_callback = {
 };
 
 static void default_error_callback_fn(const char* str, void* data) {
-    (void)data;
     fprintf(stderr, "[libsecp256k1] internal consistency check failed: %s\n", str);
     abort();
 }