patch 8.2.2315: Vim9: "enddef" as dict key misintepreted as function end

Problem:    Vim9: "enddef" as dict key misintepreted as function end.
Solution:   Check for following colon. (closes #7640)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 9f19ebd..fb37401 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -116,6 +116,14 @@
   CheckScriptFailure(lines, 'E126:', 2)
 enddef
 
+def Test_enddef_dict_key()
+  var d = {
+    enddef: 'x',
+    endfunc: 'y',
+  }
+  assert_equal({enddef: 'x', endfunc: 'y'}, d)
+enddef
+
 def ReturnString(): string
   return 'string'
 enddef