Revert "[AUD-726] Support create sender public in discovery"

[rickyrombo]

Reverts #1808
Reverts #2082

@raymondjacobson reland this once you get the right config wired up. Looks like REWARDS_MANAGER_PROGRAM_ACCOUNT isn't connected properly

ValueError: ('invalid public key input:', '')
[2021-11-20 08:27:23 +0000] [30] [INFO] Worker exiting (pid: 30)
[2021-11-20 08:27:24 +0000] [19] [ERROR] Exception in worker process
Traceback (most recent call last):
  File "/usr/lib/python3.8/site-packages/gunicorn/arbiter.py", line 583, in spawn_worker
    worker.init_process()
  File "/usr/lib/python3.8/site-packages/gunicorn/workers/geventlet.py", line 99, in init_process
    super().init_process()
  File "/usr/lib/python3.8/site-packages/gunicorn/workers/base.py", line 119, in init_process
    self.load_wsgi()
  File "/usr/lib/python3.8/site-packages/gunicorn/workers/base.py", line 144, in load_wsgi
    self.wsgi = self.app.wsgi()
  File "/usr/lib/python3.8/site-packages/gunicorn/app/base.py", line 67, in wsgi
    self.callable = self.load()
  File "/usr/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 49, in load
    return self.load_wsgiapp()
  File "/usr/lib/python3.8/site-packages/gunicorn/app/wsgiapp.py", line 39, in load_wsgiapp
    return util.import_app(self.app_uri)
  File "/usr/lib/python3.8/site-packages/gunicorn/util.py", line 358, in import_app
    mod = importlib.import_module(module)
  File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 848, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/audius-discovery-provider/src/wsgi.py", line 4, in <module>
    from src.app import create_app
  File "/audius-discovery-provider/src/app.py", line 21, in <module>
    from src.api.v1 import api as api_v1
  File "/audius-discovery-provider/src/api/v1/api.py", line 7, in <module>
    from src.api.v1.challenges import ns as challenges_ns
  File "/audius-discovery-provider/src/api/v1/challenges.py", line 14, in <module>
    from src.queries.get_attestation import (
  File "/audius-discovery-provider/src/queries/get_attestation.py", line 24, in <module>
    REWARDS_MANAGER_PROGRAM_ACCOUNT = PublicKey(
  File "/usr/lib/python3.8/site-packages/solana/publickey.py", line 35, in __init__
    raise ValueError("invalid public key input:", value)
ValueError: ('invalid public key input:', '')