Update python version in README.md

[JDDevISSC]

Since iRODS release 4.3.0 Python3 is used.

See: https://docs.irods.org/4.3.4/release_notes/#430

[korydraughn]

Thanks for the contribution.

Please update the commit message to include issue number 53. Consider adjusting the wording so that the top-level message states what the commit is about, as shown in the text.

[#53] Update python version in README.md

[alanking]

Very nice. Please adjust the commit message title to link to our "housekeeping" issue, like so:

[#53] Update README.md

Once done, we will get this in. Thanks

Edit: @korydraughn sniped me :)

[JDDevISSC]

Done

[alanking]

Excellent. Thanks!