Merge pull request github#18385 from aisgbnok/update-fork-image

Update fork button image

Author: mchammer01

assets/images/help/repository/fork_button.jpg

@@ -26,7 +26,7 @@ This tutorial uses [the Spoon-Knife project](https://github.com/octocat/Spoon-Kn
 
 1. Navigate to the `Spoon-Knife` project at https://github.com/octocat/Spoon-Knife.
 2. Click **Fork**.
-   ![Fork button](/assets/images/help/repository/fork_button.jpg)
+   ![Fork button](/assets/images/help/repository/fork_button.png)
 1. {% data variables.product.product_name %} will take you to your copy (your fork) of the Spoon-Knife repository.
 
 ## Cloning a fork

assets/images/help/repository/fork_button.png

@@ -57,7 +57,7 @@ You might fork a project to propose changes to the upstream, or original, reposi
 
 1. On {% ifversion fpt or ghec %}{% data variables.product.prodname_dotcom_the_website %}{% else %}{% data variables.product.product_location %}{% endif %}, navigate to the [octocat/Spoon-Knife](https://github.com/octocat/Spoon-Knife) repository.
 2. In the top-right corner of the page, click **Fork**.
-![Fork button](/assets/images/help/repository/fork_button.jpg)
+![Fork button](/assets/images/help/repository/fork_button.png)
 
 {% endwebui %}