net-im/py-matrix-synapse: Update to 1.150.1

• Updated USES to python:3.7+ since upstream has removed python 3.6 from the supported python versions
• Removed the test dependency on py-mock in sync with upstream requirements
• Added a new dependency on devel/py-matrix-common, a new port that provides code shared by most matrix.org projects, inlcuding synapse

PR: 260502
(cherry picked from commit c54c79c82dce9c97dc4bab972e15a6d4dd3b744a)