Version bump to 0.4.0 (#179)

Author: sachinprasadhs

keras_rs/src/version.py

@@ -1,7 +1,7 @@
 from keras_rs.src.api_export import keras_rs_export
 
 # Unique source of truth for the version number.
-__version__ = "0.4.0.dev0"
+__version__ = "0.4.0"
 
 
 @keras_rs_export("keras_rs.version")