Update database.md (parse-community#831)

Small grammar update I noticed when combing through the docs. Thanks for all truly valuable contributions you guy make.

Author: cyobrendan

_includes/parse-server/database.md

@@ -1,6 +1,6 @@
 # Database
 
-Parse Server let you use [MongoDB](https://www.mongodb.org/) or [Postgres](https://www.postgresql.org/) as a database.
+Parse Server lets you use [MongoDB](https://www.mongodb.org/) or [Postgres](https://www.postgresql.org/) as a database.
 
 The prefered database is MongoDB but Postgres is a great option if you're starting a new project and you expect to have a stable Schema.