Set default zap sampling config to nil

[psinghal20]

Which problem is this PR solving?

• Resolves Default logging shouldn't be sampled #160. Sets the default config behavior to no sampling for zap

Short description of the changes

• Changes the default sampling config for the zap logger to nil

[codecov]

Codecov Report

Merging #1460 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1460   +/-   ##
=======================================
  Coverage   99.82%   99.82%           
=======================================
  Files         173      173           
  Lines        8162     8162           
=======================================
  Hits         8148     8148           
  Misses          7        7           
  Partials        7        7

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[yurishkuro]

thanks!