patch 8.2.1777: Vim9: some assignment tests in the wrong file

Problem:    Vim9: some assignment tests in the wrong file.
Solution:   Move assignment tests to test_vim9_assign.
diff --git a/src/version.c b/src/version.c
index b3014bb..446ac55 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1777,
+/**/
     1776,
 /**/
     1775,