docs: Rename Stored Procedures to Functions consistently

This avoids confusing our RPCs with actual CREATE PROCEDURE, which we don't
support.

References https://github.com/PostgREST/postgrest-docs/issues/147

docs/tutorials/tut0.rst

@@ -11,7 +11,7 @@ PostgREST is a standalone web server which turns a PostgreSQL database into a RE
 
 .. image:: ../_static/tuts/tut0-request-flow.png
 
-To make an API we'll simply be building a database. All the endpoints and permissions come from database objects like tables, views, roles, and stored procedures. These tutorials will cover a number of common scenarios and how to model them in the database.
+To make an API we'll simply be building a database. All the endpoints and permissions come from database objects like tables, views, roles, and functions. These tutorials will cover a number of common scenarios and how to model them in the database.
 
 By the end of this tutorial you'll have a working database, PostgREST server, and a simple single-user todo list API.
 

docs/tutorials/tut1.rst

@@ -202,7 +202,7 @@ Save it to an environment variable:
 
   export WAYWARD_TOKEN="<paste new token>"
 
-PostgREST allows us to specify a stored procedure to run during attempted authentication. The function can do whatever it likes, including raising an exception to terminate the request.
+PostgREST allows us to specify a function to run during attempted authentication. The function can do whatever it likes, including raising an exception to terminate the request.
 
 First make a new schema and add the function: