Update pull_request_template.md (commons-app#1476)

* Update pull_request_template.md

* Remove Javadocs mention

* Added required/optional notes

Author: misaochan

PULL_REQUEST_TEMPLATE.md

@@ -1,15 +1,15 @@
-## Description
+## Description (required)
 
-Fixes #{GitHub issue number}
+Fixes #{GitHub issue number and title}
 
 {Describe the changes made and why they were made.}
 
-## Tests performed
+## Tests performed (required)
 
 Tested on {API level & name of device/emulator}, with {build variant, e.g. ProdDebug}.
 
-{Please test your PR at least once before submitting.}
-
-## Screenshots showing what changed
+## Screenshots showing what changed (optional)
 
 {Only for user interface changes, otherwise remove this section. See [how to take a screenshot](https://android.stackexchange.com/questions/1759/how-to-take-a-screenshot-with-an-android-device)}
+
+_Note: Please ensure that you have read CONTRIBUTING.md if this is your first pull request._