V5 Amplify installation docs do not specify V5 version

[david-mcafee]

Describe the bug
Our V5 docs currently ask the user to install the latest version of aws-amplify (which is currently V6). Everywhere our docs instruct the user to install Amplify should be pinned to a V5 tag (i.e. aws-amplify@stable-v5). Because we share code snippets between V5 and V6, this is not a trivial update.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://docs.amplify.aws/react-native/prev/build-a-backend/graphqlapi/set-up-graphql-api/#configure-your-application
2. Observe npm install aws-amplify without tagged version.

Expected behavior
We should use the V5 tag everywhere we ask users to install Amplify in the V5 docs.

Screenshots
If applicable, add screenshots to help explain your problem.

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]

Additional context
Add any other context about the problem here.

[david-mcafee]

Thanks for updating this, @israx!