patch 8.2.1320: Vim9: cannot declare some single letter variables

Problem:    Vim9: cannot declare some single letter variables.
Solution:   Do not recognize a colon for a namespace for single letter
            variables. (closes #6547)
diff --git a/src/version.c b/src/version.c
index 4b53df3..b81ac06 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1320,
+/**/
     1319,
 /**/
     1318,