Update openms-user-tutorial.md (#204)

* Update openms-user-tutorial.md

I have reviewed the tutorial and identified a few minor grammatical and spelling errors that I believe are worth correcting.

* Update docs/tutorials-and-quickstart-guides/openms-user-tutorial.md

Co-authored-by: Timo Sachsenberg <[email protected]>

* Apply suggestions from code review

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Co-authored-by: Samuel Wein <[email protected]>
Co-authored-by: Timo Sachsenberg <[email protected]>