test: fix logging tests

[simonz130]

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Fixes #426 ☕️

[codecov]

Codecov Report

Merging #493 (f12019c) into master (9b0423f) will increase coverage by 0.01%.
The diff coverage is 20.00%.

@@             Coverage Diff              @@
##             master     #493      +/-   ##
============================================
+ Coverage     79.30%   79.32%   +0.01%     
  Complexity      745      745              
============================================
  Files            44       44              
  Lines          4253     4252       -1     
  Branches        287      286       -1     
============================================
  Hits           3373     3373              
  Misses          692      692              
+ Partials        188      187       -1     

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/com/google/cloud/logging/SinkInfo.java	80.69% <0.00%> (ø)	19.00 <0.00> (ø)
.../java/com/google/cloud/logging/LoggingHandler.java	74.31% <100.00%> (+0.67%)	22.00 <0.00> (ø)

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