[Tunnels] docs: update deprecated cloudflare_tunnel resource

[Pedr0Rocha]

Summary

Cloudflare tunnels terraform docs use cloudflare_tunnel and cloudflare_tunnel_config resources. When you run this in terraform you get:

│ Warning: Deprecated Resource
│ 
│ `cloudflare_tunnel` is now deprecated and will be removed in the next major
│ version. Use `cloudflare_zero_trust_tunnel_cloudflared` instead.

and

Warning: Deprecated Resource
│ 
│ `cloudflare_tunnel_config` is now deprecated and will be removed in the
│ next major version. Use `cloudflare_zero_trust_tunnel_cloudflared_config`
│ instead.

Documentation checklist

• The documentation style guide has been adhered to.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

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[ibrahimkhled]