patch 8.2.1708: Vim9: error message for function has unpritable characters

Problem:    Vim9: error message for function has unpritable characters.
Solution:   use printable_func_name(). (closes #6965)
diff --git a/src/version.c b/src/version.c
index fd880f5..2701c79 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1708,
+/**/
     1707,
 /**/
     1706,