docs: update discord link on readme and remove old image files (#15350)

## Description

Updated the expired links on the Readme file and removed unused image assets from the root directory. 

## Fixes # (issue)

Expired links on Readme. 

## Type of change

- Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

I've reviewed the content. 

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my own code
- [ ] I have commented on my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my feature works
- [ ] New and existing unit tests pass locally with my changes

README.md

@@ -106,7 +106,7 @@ Check out some real applications that can be built with Appsmith:
 - 📄 [Application Tracking System App](https://app.appsmith.com/applications/5f43bce13697fd5df1c52ce4/pages/5f43c39c3697fd5df1c52d50/?utm_source=github&utm_medium=direct&utm_content=appsmith_apps&utm_campaign=null&utm_term=appsmith_apps)
 - 📦 [All Sample Apps](https://docs.appsmith.com/sample-apps?utm_source=github&utm_medium=direct&utm_content=appsmith_apps&utm_campaign=null&utm_term=appsmith_apps)
 
-- 🌟 Made something cool? [Share it with the community](https://discord.gg/Tx395War)
+- 🌟 Made something cool? [Share it with the community](https://discord.gg/rBTTVJp)
   <br><br>
 
 ## Tutorials