docs: remove outdated section from dashboard

Author: IgnisDa

README.md

@@ -29,11 +29,6 @@
 Ryot (**R**oll **Y**our **O**wn **T**racker), pronounced "riot", aims to be the only self
 hosted tracker you will ever need!
 
-## IMPORTANT NOTE FOR `v3.*` USERS
-
-If you were using `v3.*` of Ryot, please read the
-[migration guide](https://ignisda.github.io/ryot/migration.html#from-v3-to-v4) for instructions.
-
 ## 💻 Demo
 
 You can use the demo instance hosted on [Fly.io](https://ryot.fly.dev). Login