patch 8.2.0913: code for resetting v:register is duplicated

Problem:    Code for resetting v:register is duplicated.
Solution:   Add reset_reg_var().
diff --git a/src/version.c b/src/version.c
index ea3f6a4..2b9bd77 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    913,
+/**/
     912,
 /**/
     911,