Fix lavender typo

What does this MR do and why?

There are a couple places where lavender is misspelled as 'lavendar' (source). In other places it is spelled correctly (source). I believe -er is the correctly spelling for these reasons:

• Merriam-Webster thinks so (source)
• Searching for the -ar doesn't give any convincing results (Startpage, DuckDuckGo, Brave)
• Subjectively, my spell checkers agree

Screenshots or screen recordings

I'm hoping this doesn't count as a UI change 🤞

How to set up and validate locally

I'm also hoping this isn't necessary for this spelling correction 🤞

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.