Improve wording in di_in_python.rst

Author: rmk135

docs/introduction/di_in_python.rst

@@ -150,7 +150,7 @@ What does the Dependency Injector do?
 -------------------------------------
 
 With the dependency injection pattern objects loose the responsibility of assembling
-the dependencies. The ``Dependency Injector`` absorbs that responsibilities.
+the dependencies. The ``Dependency Injector`` absorbs that responsibility.
 
 ``Dependency Injector`` helps to assemble and inject the dependencies.