docs: fix simple typo, retruns -> returns

[timgates42]

There is a small typo in mycroft/skills/skill_data.py.

Should read returns rather than retruns.

Semi-automated pull request generated by
https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

[devops-mycroft]

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[devops-mycroft]

Voight Kampff Integration Test Succeeded (Results)

[forslund]

Thanks for fixing this @timgates42, as soon as the CLA is completed we can merge it :) Happy Holidays!

[timgates42]

Thanks @forslund have filled it in now

[krisgesling]

Thanks Tim - CLA received :)