bump pytest from 6.0.2 to 6.2.5

pytest 6.2.5 adds support for Python 3.10. [Link](pytest-dev/pytest#8494) to relevant PR.

requirements-test.txt

@@ -1,4 +1,4 @@
-pytest==6.0.2
+pytest==6.2.5
 pytest-django==3.10.0
 psycopg2-binary==2.8.6
 pytest-cov==2.10.1