use --no-package-lock in npm

[mansona]

This removes the warning that npm gives when you try to use the deprecated --no-shrinkwrap option 👍

--no-package-lock was added in npm 5 so it's been recommended for a long time!

[codecov]

Codecov Report

Merging #961 (00d4a6e) into master (9d9763a) will increase coverage by 0.03%.
The diff coverage is 100.00%.

❗ Current head 00d4a6e differs from pull request most recent head b52721e. Consider uploading reports for the commit b52721e to get more accurate results

@@            Coverage Diff             @@
##           master     #961      +/-   ##
==========================================
+ Coverage   94.59%   94.63%   +0.03%     
==========================================
  Files          17       17              
  Lines         555      559       +4     
==========================================
+ Hits          525      529       +4     
  Misses         30       30              

Files Changed	Coverage Δ
lib/dependency-manager-adapters/npm.js	98.46% <100.00%> (+0.04%)	⬆️

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