Removed double 'a' word in tutorial part 1.
Tutorial - Part 1 - Getting Started
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-This tutorial provides a a very gradual introduction to event-sourced aggregates and
+This tutorial provides a very gradual introduction to event-sourced aggregates and
applications, explaining just enough on the mechanics of this library to help users
of the library understand how things work. It expands and explains the
:ref:`Synopsis <Synopsis>`, and prepares new users of the library for reading
