log: Remove redundant log context.

[bgrozev]

The Relay already has its ID in the context resulting in:
relayId=jvb-foo-bar relay-id=jvb-foo-bar

[codecov]

Codecov Report

Merging #2023 (52356da) into master (9eefa65) will decrease coverage by 0.06%.
The diff coverage is n/a.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2023      +/-   ##
============================================
- Coverage     42.57%   42.52%   -0.06%     
+ Complexity     1679     1676       -3     
============================================
  Files           326      326              
  Lines         17007    17006       -1     
  Branches       2244     2244              
============================================
- Hits           7240     7231       -9     
- Misses         9055     9071      +16     
+ Partials        712      704       -8     

Impacted Files	Coverage Δ
...g/jitsi/videobridge/relay/RelayMessageTransport.kt	7.46% <ø> (-0.46%)	⬇️

... and 6 files with indirect coverage changes

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