docs: update test wallet info

[melissahenderson]

This PR fixes #509

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Latest commit: 33f7297

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[brad-dow]

Just a few things I noticed:

• Number 3 under "Create an account on the test wallet" - Perhaps missing a period before "Click the arrowhead."
• Is it worth defining KYC or is this a known acronym to this audience?
• Number 1 under "Create and fund a wallet account" - Change New Account to New account.
• Number 3 under "Add a payment pointer to your wallet account" - Styling of "payment pointer name" doesn't match the screenshot (it doesn't necessarily have to - just drawing attention to it).