patch 8.2.1313: Vim9 script: cannot assign to environment variable

Problem:    Vim9 script: cannot assign to environment variable.
Solution:   Recognize environment variable assignment. (closes #6548)
            Also options and registers.
diff --git a/src/version.c b/src/version.c
index 26bd7ac..fce9218 100644
--- a/src/version.c
+++ b/src/version.c
@@ -755,6 +755,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1313,
+/**/
     1312,
 /**/
     1311,