[CLEANUP] Remove DEPRECATE_TEMPLATE_ACTION (#20882)

* Removed tests targeting DEPRECATE_TEMPLATE_ACTION

* Remove code deprecated via DEPRECATE_TEMPLATE_ACTION

* Restored non-modifier bits of the action modifier source file

* Update packages/@ember/-internals/glimmer/lib/resolver.ts

* Update packages/@ember/-internals/glimmer/lib/resolver.ts

* Update packages/@ember/-internals/glimmer/lib/resolver.ts

* Update packages/@ember/-internals/glimmer/lib/resolver.ts

* Removed node test with action modifier

---------

Co-authored-by: Katie Gengler <[email protected]>

Author: tcjr

packages/@ember/-internals/deprecations/index.ts

@@ -102,16 +102,6 @@ export const DEPRECATIONS = {
       ).toLowerCase()}-from-ember`,
     });
   },
-  DEPRECATE_TEMPLATE_ACTION: deprecation({
-    id: 'template-action',
-    url: 'https://deprecations.emberjs.com/id/template-action',
-    until: '6.0.0',
-    for: 'ember-source',
-    since: {
-      available: '5.9.0',
-      enabled: '5.9.0',
-    },
-  }),
   DEPRECATE_COMPONENT_TEMPLATE_RESOLVING: deprecation({
     id: 'component-template-resolving',
     url: 'https://deprecations.emberjs.com/id/component-template-resolving',