Improve interest-is-interesting exercise's concept introduction

[NateEag]

Fixes some grammar, removes some unneeded words, and clarifies a point or two.

[github-actions]

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[NateEag]

@iHiD Applied your suggestion - anything else I should do here?

[ErikSchierboom]

One sec. I'll look at this soon

[NateEag]

Thanks @ErikSchierboom !