docs: Use sentence case for title names. (#1258)

Ref: https://docs-docs.netlify.com/docs/docs/formatting.html#sentence-case

docs/source/features/cdn.md

@@ -1,5 +1,5 @@
 ---
-title: CDN Integration
+title: CDN integration
 description: Getting content delivery networks to cache GraphQL responses
 ---
 

docs/source/features/data-sources.md

@@ -1,5 +1,5 @@
 ---
-title: Data Sources
+title: Data sources
 description: Caching Partial Query Results
 ---
 

docs/source/features/file-uploads.md

@@ -1,6 +1,6 @@
 ---
-title: File Uploads
-description: Implementing File Uploads on Apollo Server
+title: File uploads
+description: Implementing file uploads on Apollo Server
 ---
 
 File uploads are a requirement for many applications. Apollo Server supports the [GraphQL multipart request spec](https://github.com/jaydenseric/graphql-multipart-request-spec) for uploading files as mutation arguments using [apollo-upload-server](https://github.com/jaydenseric/apollo-upload-server).

docs/source/features/metrics.md

@@ -1,5 +1,5 @@
 ---
-title: Monitoring and Metrics
+title: Monitoring and metrics
 description: How to monitor Apollo Server's performance
 ---
 

docs/source/schemas/types.md

@@ -1,5 +1,5 @@
 ---
-title: Schema Types
+title: Schema types
 description: How to write your types, expose your data, and keep it all working great
 ---