few grammar fixes

Author: osamaakb

module3-crud-and-data-models/r1.1-principles-of-setting-up-your-schema/README.md

@@ -26,7 +26,7 @@ One of the key points to establish a good schema design (especially, if you are
 
 #### When to `Embed`:
 
-- Retrive all data in a single query.
+- To retrive all data in a single query.
 - Avoid expense JOINs or $lookups.
 - Update all data with a single operation.
 - In one-to-one or one-to-many relationships between documents.

module3-crud-and-data-models/r3-model-view-controller/README.md

@@ -11,7 +11,6 @@ app-name-here
  |- db
  |- Models
  |- node_modules
- |- Services
 .gitignore
 index.js
 package.json