fix(site): display tasks link when no templates contain an AI task (#19184)

Fixes https://github.com/coder/coder/issues/19059

This change ensures we always show the "Tasks" link, even when a deployment doesn't yet have a tasks template set up.

coderd/database/queries/templateversions.sql

@@ -234,7 +234,3 @@ FROM
 WHERE
 	template_versions.id IN (archived_versions.id)
 RETURNING template_versions.id;
-
--- name: HasTemplateVersionsWithAITask :one
--- Determines if the template versions table has any rows with has_ai_task = TRUE.
-SELECT EXISTS (SELECT 1 FROM template_versions WHERE has_ai_task = TRUE);