patch 8.2.0368: Vim9: import that redefines local variable does not fail

Problem:    Vim9: import that redefines local variable does not fail.
Solution:   Check for already defined symbols.
diff --git a/src/version.c b/src/version.c
index 0c0cebe..b02d56a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    368,
+/**/
     367,
 /**/
     366,