Update "verify transaction" example for rule ideas

[TheMrMilchmann]

See semgrep/semgrep#9532 for context. This PR simply realigns the docs example with the README example.

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Thanks for improving Semgrep Docs 😀

Please ensure

• A subject matter expert (SME) reviews the content
• A technical writer reviews the content or PR
• This change has no security implications or else you have pinged the security team
• Redirects are added if the PR changes page URLs
• If you have changed any header tag links (doc/#this-kind-of-anchor), update all instances of that link

[s-santillan]

@TheMrMilchmann thank you for your contribution. We'll sync the docs with the readme once the PR is merged :)