Documentation mistake in the pyplot introductory tutorial

[leonprou]

Bug report

In the introductory tutorial, you can read " The subplot() command specifies numrows, numcols, fignum where fignum ranges from 1 to numrows*numcols".
I'm interpreting fignum as figure number, which is a wrong cause the third argument is plot_number, it's easily seen in the docs of subplot

To fix, just need replace here fignum to plot_number.

[leonprou]

@dsblank thanks for the tags. It's really small, so I can make a PR if you're interested.

[tacaswell]

@leonprou Please do! We ❤️ documentation PRs!

[surana-mudit]

Hey @leonprou , I am a new contributor to this repo, I would like to make a PR for this issue as it is my first issue

[leonprou]

@surana-mudit ok, go for it 👍

[dstansby]

Fixed by #10055