fix broken icon (discord#7177)

Author: shaydewael

docs/activities/Building_An_Activity.mdx

@@ -687,7 +687,7 @@ This is an intentionally simple example to get you started with the communicatio
   <Card title="Development Guides" link="#DOCS_DEVELOPER_TOOLS_COMMUNITY_RESOURCES" icon="WrenchIcon">
     Follow our Activities Development Guides for suggested development practices and considerations.
   </Card>
-  <Card title="Sample Activity Projects" link="https://github.com/discord/embedded-app-sdk-examples" icon="GithubNeutralIcon">
+  <Card title="Sample Activity Projects" link="https://github.com/discord/embedded-app-sdk-examples" icon="ForumIcon">
      Try out the full range of Embedded App SDK features in the playground app, or explore some of the other examples
   </Card>
   <Card title="Discord Developers" link="https://discord.gg/discord-developers" icon="GlobeEarthIcon">