Fix link to next-image-to-legacy-image codemod

[IDrumsey]

For the upgrade guide for 12 to 13, there's a link pointing to the next-image-to-legacy-image, but the fragment link isn't correct. See this which links to #rename-instances-of-nextimage which doesn't look like it goes anywhere.

Bug

• Related issues linked using fixes #number
• Integration tests added
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Feature

• Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
• Related issues linked using fixes #number
• e2e tests added
• Documentation added
• Telemetry added. In case of a feature if it's used or not.
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Documentation / Examples

• Make sure the linting passes by running pnpm build && pnpm lint
• The "examples guidelines" are followed from our contributing doc

Do I need to run the pnpm build && pnpm lint for this?

[ijjk]

Good catch, thanks!