Remove obsolete settings from docker homeserver.yaml

[richvdh]

These aren't used, because we have a log_config setting.

[codecov-io]

Codecov Report

Merging #4261 into develop will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #4261      +/-   ##
===========================================
+ Coverage    73.51%   73.52%   +0.01%     
===========================================
  Files          298      298              
  Lines        29819    29819              
  Branches      4881     4881              
===========================================
+ Hits         21921    21925       +4     
+ Misses        6460     6458       -2     
+ Partials      1438     1436       -2

Impacted Files	Coverage Δ
synapse/app/homeserver.py	57.28% <0%> (+0.33%)	⬆️
synapse/state/v1.py	92.24% <0%> (+1.55%)	⬆️
synapse/util/file_consumer.py	82.45% <0%> (+1.75%)	⬆️

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