chore: remove package-lock.json

[mfranzke]

Summary of changes:

Removing the only remaining package-lock.json file to prevent any problems, as described on the console:

warning package-lock.json found. Your project contains lock files generated by tools other than Yarn. It is advised not to mix package managers in order to avoid resolution inconsistencies caused by unsynchronized lock files. To clear this warning, remove package-lock.json.

In our documentation we're mainly focused on yarn usage and even also include a yarn.lock file in root.

[JosefBredereck]

PR was released with v5.16.0