patch 8.2.3991: Vim9: error when extending dict<any>

Problem:    Vim9: error when extending dict<any> with another type that it was
            initialized with.
Solution:   Also set the type for dict<any> if the initializer has a more
            specific type. (closes #9461)
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 2ee1a93..df27dba 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -2143,6 +2143,11 @@
     CheckDefAndScriptFailure(['map(test_null_channel(), "1")'], ['E1013: Argument 1: type mismatch, expected list<any> but got channel', 'E1251: List, Dictionary, Blob or String required for argument 1'])
   endif
   CheckDefAndScriptFailure(['map(1, "1")'], ['E1013: Argument 1: type mismatch, expected list<any> but got number', 'E1251: List, Dictionary, Blob or String required for argument 1'])
+
+  # type of dict remains dict<any> even when type of values changes
+  var d: dict<any> = {a: 0}
+  d->map((k, v) => true)
+  d->map((k, v) => 'x')
 enddef
 
 def Test_map_failure()