fix: use free versions of the icons temporarily (#39598)

docs/_sidebar.md

@@ -1,6 +1,6 @@
-- **<i class="fad fa-hourglass-start"></i> Getting Started**
+- **<i class="fas fa-hourglass-start"></i> Getting Started**
   - [Introduction](/index.md 'Contribute to the freeCodeCamp.org Community')
-- **<i class="fad fa-code"></i> Code Contribution**
+- **<i class="fas fa-code"></i> Code Contribution**
   - [Work on coding challenges](/how-to-work-on-coding-challenges.md)
   - [Help with video challenges](/how-to-help-with-video-challenges.md)
   - [Set up freeCodeCamp locally](/how-to-setup-freecodecamp-locally.md)
@@ -12,7 +12,7 @@
 
 ---
 
-- **<i class="fad fa-plane-alt"></i> Flight Manuals** (for Staff & Mods)
+- **<i class="fas fa-plane"></i> Flight Manuals** (for Staff & Mods)
   - [Moderator Handbook](/flight-manuals/moderator-handbook.md)
   - [Reply Templates](/flight-manuals/using-reply-templates.md)
   - [DevOps Overview](/devops.md)
@@ -20,14 +20,14 @@
 
 ---
 
-- **<i class="fad fa-language"></i> 中文社区贡献指南**
+- **<i class="fas fa-language"></i> 中文社区贡献指南**
   - [成为专栏作者](/chinese-guides/news-author-application.md)
   - [文章翻译计划](/chinese-guides/news-translations.md)
   - [视频翻译计划](/chinese-guides/video-translations.md)
 
 ---
 
-- **<i class="fad fa-user-friends"></i> Our Community**
+- **<i class="fas fa-user-friends"></i> Our Community**
   - [**<i class="fab fa-github"></i> GitHub Repository**](https://github.com/freecodecamp/freecodecamp)
   - [**<i class="fab fa-discourse"></i> Contributors category on Forum**](https://freecodecamp.org/forum/c/contributors)
   - [**<i class="fab fa-gitter"></i> Contributors chat room on Gitter**](https://gitter.im/FreeCodeCamp/Contributors)