www/py-bleach: Update to 2.1.3 [1]

• Update TEST_DEPENDS (upstream switched from nose -> pytest)

This version also fixes notifications in the existing version of
net-im/py-matrix-synapse. [2]

Changelog:

https://github.com/mozilla/bleach/blob/v2.1.3/CHANGES

PR: 226851 [1][2]
Submitted by: mi
MFH: 2018Q2