patch 8.1.1021: pyeval() and py3eval() leak memory

Problem:    pyeval() and py3eval() leak memory.
Solution:   Do not increase the reference count twice. (Ozaki Kiichi,
            closes #4129)
diff --git a/src/version.c b/src/version.c
index c336046..bd02fa5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -780,6 +780,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1021,
+/**/
     1020,
 /**/
     1019,