Fix image suffix mismatch in description

[zm999999]

Fix image suffix mismatch in description

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[parlough]

Thanks for catching and fixing this! I see there's still a few other png suffix examples remaining.

What do you think about updating them all to .png? I think that's likely the more common file type.

[zm999999]

@parlough Thank you for pointing that out! I will update the examples to .png.