Fix missing known usage data event

When implementing CI template usage data tracking, we missed one
template event, causing errors. This was missed during tests because the
shared example we relied on stubbed the `track_event` method, which is
responsible for the failing validation.

changelogs/unreleased/add-missing-known-event-ecs-deploy-template.yml

+---
+title: Fix missing known usage data event
+merge_request: 53729
+author:
+type: fixed

lib/gitlab/usage_data_counters/known_events/common.yml

@@ -578,6 +578,11 @@
   redis_slot: ci_templates
   aggregation: weekly
   feature_flag: usage_data_track_ci_templates_unique_projects
+- name: p_ci_templates_aws_deploy_ecs
+  category: ci_templates
+  redis_slot: ci_templates
+  aggregation: weekly
+  feature_flag: usage_data_track_ci_templates_unique_projects
 - name: p_ci_templates_auto_devops_build
   category: ci_templates
   redis_slot: ci_templates

spec/support/shared_examples/controllers/unique_hll_events_examples.rb

@@ -7,7 +7,11 @@
 
 RSpec.shared_examples 'tracking unique hll events' do |feature_flag|
   it 'tracks unique event' do
-    expect(Gitlab::UsageDataCounters::HLLRedisCounter).to receive(:track_event).with(target_id, values: expected_type)
+    expect(Gitlab::UsageDataCounters::HLLRedisCounter).to(
+      receive(:track_event)
+        .with(target_id, values: expected_type)
+        .and_call_original # we call original to trigger additional validations; otherwise the method is stubbed
+    )
 
     request
   end