update terminal commands per framework for "Separate frontend and backend"

[cwomack]

Describe the bug
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The "deploy the frontend" section (here) within the Separate Frontend and Backend Teams pages within the Amplify docs shows npm create next-app@14 for all frameworks. Needs to be updated per framework.

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3. Scroll down to '....'
4. See error

Expected behavior
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

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