chore(docs): removed install instructions from docs

[boyney123]

Checklist

This removes Wing installation instructions from the docs (as we now have a new page). But this PR requires https://github.com/winglang/docsite/pull/1041 to be merged first.

• [x] Title matches Winglang's style guide
• [x] Description explains motivation and solution
• [ ] Tests added (always)
• [ ] Docs updated (only required for features)
• [ ] Added pr/e2e-full label if this feature requires end-to-end testing

By submitting this pull request, I confirm that my contribution is made under the terms of the Wing Cloud Contribution License.

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