patch 8.2.1625: compiler warning for use of fptr_T

Problem:    Compiler warning for use of fptr_T.
Solution:   Make the type less strict.
diff --git a/src/regexp.c b/src/regexp.c
index 375731c..22b2d17 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -1691,9 +1691,9 @@
  * We should define ftpr as a pointer to a function returning a pointer to
  * a function returning a pointer to a function ...
  * This is impossible, so we declare a pointer to a function returning a
- * pointer to a function returning void. This should work for all compilers.
+ * void pointer. This should work for all compilers.
  */
-typedef void (*(*fptr_T)(int *, int))();
+typedef void (*(*fptr_T)(int *, int));
 
 static int vim_regsub_both(char_u *source, typval_T *expr, char_u *dest, int copy, int magic, int backslash);