Update payload_interceptors.go

[bradywatkinson]

Update incorrect logging message in PayloadUnaryServerInterceptor from:
"server response payload logged as grpc.request.content field"
to
"server response payload logged as grpc.response.content field"

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[codecov-io]

Codecov Report

Merging #170 into master will decrease coverage by 0.67%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #170      +/-   ##
==========================================
- Coverage   73.47%   72.79%   -0.68%     
==========================================
  Files          36       36              
  Lines        1327     1327              
==========================================
- Hits          975      966       -9     
- Misses        303      311       +8     
- Partials       49       50       +1

Impacted Files	Coverage Δ
logging/logrus/payload_interceptors.go	84.12% <100%> (ø)	⬆️
retry/retry.go	73.33% <0%> (-5%)	⬇️

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[domgreen]

This change is good, but could you make the same change in logging/zap/payload_interceptors.go.