Grammer correction - SPFX setting up environment.

The word 'if' is changed to 'is' on the SPFX docs page for setting up your environment.

Author: nanddeepn

docs/spfx/set-up-your-development-environment.md

@@ -1,7 +1,7 @@
 ---
 title: Set up your SharePoint Framework development environment
 description: Use Visual Studio or your own custom development environment to build SharePoint Framework solutions. You can use a Mac, PC, or Linux.
-ms.date: 07/02/2020
+ms.date: 07/25/2020
 ms.prod: sharepoint
 localization_priority: Priority
 ms.custom: scenarios:getting-started
@@ -62,7 +62,7 @@ The SharePoint Framework development and build toolchain leverages various popul
 
 ### Install Gulp
 
-[Gulp](https://gulpjs.com) if a JavaScript-based task runner used to automate repetitive tasks. The SharePoint Framework build toolchain uses Gulp tasks to build projects, create JavaScript bundles, and the resulting packages used to deploy solutions.
+[Gulp](https://gulpjs.com) is a JavaScript-based task runner used to automate repetitive tasks. The SharePoint Framework build toolchain uses Gulp tasks to build projects, create JavaScript bundles, and the resulting packages used to deploy solutions.
 
 Enter the following command to install Gulp: