[PATCH 1 of 3 topic-experiment] tutorial: use rm instead of 'hg rm' for an untracked temporary file

[Boris Feld]

`On Sun, 2017-07-09 at 15:44 +0300, Josef 'Jeff' Sipek wrote:
> # HG changeset patch
> # User Josef 'Jeff' Sipek <jeffpc at josefsipek.net>
> # Date 1499599224 -10800
> #      Sun Jul 09 14:20:24 2017 +0300
> # Branch stable
> # Node ID db3830646e34220cfcac0837a33f9a8503dea5d2
> # Parent  61e73c8fe169717105e832b23086683848a9ef53
> tutorial: use rm instead of 'hg rm' for an untracked temporary file
> 
queued, thank you very much for your contribution!