deps: update protobuf.version to v3.11.4

[renovate-bot]

This PR contains the following updates:

Package	Update	Change
com.google.protobuf:protobuf-java-util	patch	3.11.3 -> 3.11.4
com.google.protobuf:protobuf-java	patch	3.11.3 -> 3.11.4

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[codecov]

Codecov Report

Merging #202 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #202      +/-   ##
============================================
+ Coverage     82.23%   82.25%   +0.01%     
  Complexity      983      983              
============================================
  Files            99       99              
  Lines          6040     6040              
  Branches        332      332              
============================================
+ Hits           4967     4968       +1     
+ Misses          896      895       -1     
  Partials        177      177

Impacted Files	Coverage Δ	Complexity Δ
...om/google/cloud/bigtable/emulator/v2/Emulator.java	60.86% <0%> (+0.86%)	14% <0%> (ø)	⬇️

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