Bump version to 3.3.4-stable

Thanks to all contributors! <3

version.py

@@ -3,7 +3,7 @@ name = "Godot Engine"
 major = 3
 minor = 3
 patch = 4
-status = "rc"
+status = "stable"
 module_config = ""
 year = 2021
 website = "https://godotengine.org"