chore: update license headers

[stephenplusplus]

Builds were getting mad about these license headers!

[stephenplusplus]

@JustinBeckwith the header-check task is thrown off by the string-embedded license tag:

.jsdoc.js has an invalid copyright holder: Google LLC',

[JustinBeckwith]

Hah. @chingor13 can you take a look?

[codecov]

Codecov Report

Merging #256 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #256      +/-   ##
=========================================
+ Coverage   97.05%   97.1%   +0.04%     
=========================================
  Files           1       1              
  Lines         612     621       +9     
  Branches       87      87              
=========================================
+ Hits          594     603       +9     
  Misses         16      16              
  Partials        2       2

Impacted Files	Coverage Δ
src/index.ts	97.1% <100%> (+0.04%)	⬆️

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[chingor13]

Short term, googleapis/repo-automation-bots#30 should let this pass. Long term, we'll want to limit the search to the license header section. Filed googleapis/repo-automation-bots#32 to track