docs: change titles to sentence case (#21620)

PR Close #21620

aio/content/guide/service-worker-communications.md

@@ -1,4 +1,4 @@
-# Service Worker Communication
+# Service worker communication
 
 Importing `ServiceWorkerModule` into your `AppModule` doesn't just register the service worker, it also provides a few services you can use to interact with the service worker and control the caching of your app.
 

aio/content/guide/service-worker-config.md

@@ -1,6 +1,6 @@
 {@a glob}
 
-# Service Worker Configuration
+# Service worker configuration
 
 #### Prerequisites
 

aio/content/guide/service-worker-devops.md

@@ -1,4 +1,4 @@
-# Service Worker in Production
+# Service worker in production
 
 This page is a reference for deploying and supporting production apps that use the Angular service worker. It explains how the Angular service worker fits into the larger production environment, the service worker's behavior under various conditions, and available recourses and fail-safes.
 

aio/content/guide/service-worker-getting-started.md

@@ -1,4 +1,4 @@
-# Getting Started with Service Workers
+# Getting started with service workers
 
 #### Prerequisites
 

aio/content/guide/service-worker-intro.md

@@ -1,4 +1,4 @@
-# Angular Service Worker Introduction
+# Angular service worker introduction
 
 Service workers augment the traditional web deployment model and empower applications to deliver a user experience with the reliability and performance on par with natively-installed code.