Fix double variables showing up in thread and post help.

docs/changelog/7.x.x.txt

@@ -1,4 +1,5 @@
 7.7.3
+ - fixed #10094: double explanation in thread help
 
 7.7.2
  - fixed #10056: YUI javascripts included while adminOff (BNC)

lib/WebGUI/Help/Asset_Post.pm

@@ -136,11 +136,7 @@ our $HELP = {
         private => 1,
         title   => 'post asset variables title',
         body    => '',
-        isa     => [
-            {   tag       => 'asset template asset variables',
-                namespace => 'Asset'
-            },
-        ],
+        isa     => [ ],
         variables => [
             { 'name' => 'storageId' },
             { 'name' => 'threadId' },