fix(deps): update dependency @grpc/proto-loader to ^0.4.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	References
@​grpc/proto-loader	dependencies	minor	^0.3.0 -> ^0.4.0	homepage, source

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Release Notes

grpc/grpc-node

v0.4.0

Compare Source

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[codecov-io]

Codecov Report

Merging #298 into master will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #298      +/-   ##
==========================================
+ Coverage   95.16%   95.19%   +0.03%     
==========================================
  Files         124      124              
  Lines        8354     8354              
  Branches      622      622              
==========================================
+ Hits         7950     7953       +3     
+ Misses        404      401       -3

Impacted Files	Coverage Δ
src/stackdriver-monitoring.ts	84.21% <0%> (+3.15%)	⬆️

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