patch 8.2.0558: Vim9: dict code not covered by tests

Problem:    Vim9: dict code not covered by tests.
Solution:   Remove dead code, adjust test case.
diff --git a/src/version.c b/src/version.c
index f1e274b..eeec3e9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    558,
+/**/
     557,
 /**/
     556,