Remove deprecated Templar.set_available_variables() (#75836)

Fixes #75828

changelogs/fragments/75828-remove-deprecated-set_available_variables.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - Remove deprecated ``Templar.set_available_variables()`` method (https://github.com/ansible/ansible/issues/75828)

lib/ansible/template/__init__.py

@@ -776,13 +776,6 @@ class Templar:
         self._available_variables = variables
         self._cached_result = {}
 
-    def set_available_variables(self, variables):
-        display.deprecated(
-            'set_available_variables is being deprecated. Use "@available_variables.setter" instead.',
-            version='2.13', collection_name='ansible.builtin'
-        )
-        self.available_variables = variables
-
     @contextmanager
     def set_temporary_context(self, **kwargs):
         """Context manager used to set temporary templating context, without having to worry about resetting