chore: fixes the link to namespace implementation (#3653)

This link was previously fixed, but apparently, the file for namespace
implementation has been moved again (the directory name has changed).
Hence, here is the new fix.

specs/src/specs/namespace.md

@@ -94,7 +94,8 @@ Among the potential consequences is the _Woods Attack_, as elaborated in this fo
 
 ## Implementation
 
-See [go-square/namespace](https://github.com/celestiaorg/go-square/blob/main/shares/namespace.go).
+See the [namespace implementation in go-square](https://github.com/celestiaorg/go-square/blob/be3c2801e902a0f90f694c062b9c4e6a7e01154e/namespace/namespace.go).
+For the most recent version, which may not reflect the current specifications, refer to [the latest namespace code](https://github.com/celestiaorg/go-square/blob/main/share/namespace.go).
 
 ## Go Definition