py/bitbox02: lower version number that was erroneously bumped

The last tagged and released version is 5.3.0. We accidentally bumped
the major version twice. The next version is going to be 6.0.0.

Author: benma

py/bitbox02/bitbox02/bitbox02/__init__.py

@@ -16,7 +16,7 @@
 from __future__ import print_function
 import sys
 
-__version__ = "7.0.0"
+__version__ = "6.0.0"
 
 if sys.version_info.major != 3 or sys.version_info.minor < 6:
     print(