Update the link to the v4 docs (#196)

The v4 branch no longer exists, to link to the v4.1.0 tag instead.

readme.md

@@ -1,6 +1,6 @@
 # Zora
 
-If you wish to read the documentation for the older version v4, please refer to the [v4 branch](https://github.com/lorenzofox3/zora/tree/v4), the migration path will be available in the [relevant discussion](https://github.com/lorenzofox3/zora/discussions/99)
+If you wish to read the documentation for the older version v4, please refer to the [v4.1.0 tag](https://github.com/lorenzofox3/zora/tree/v4.1.0), the migration path will be available in the [relevant discussion](https://github.com/lorenzofox3/zora/discussions/99)
 
 All the projects related to [zora](./zora), the testing library