fix: required PHP extentions

[kenjis]

Description

• update the docs
• remove curl and xml from required PHP extension check in CodeIgniter

Checklist:

• Securely signed commits
• [] Component(s) with PHPDoc blocks, only if necessary or adds value
• [] Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[cijagani]

@kenjis i think CURL PHP extention is required.

https://www.codeigniter.com/user_guide/libraries/curlrequest.html?highlight=curl#

[kenjis]

@cijagani Yes, ext-curl is required if you use CURLRequest.
But if you don't use CURLRequest, you don't need it.

[cijagani]

we should keep curl-extenstion as required in doc. cz of if someone use CURLRequest and curl extenstion is not installed then it will throw exeptions.

[kenjis]

It is listed:
https://github.com/codeigniter4/CodeIgniter4/blob/fc0a497f3939b0a3138d36e82d0fe15ce8ee0cba/user_guide_src/source/intro/requirements.rst

[MGatner]

We should consider moving CURLRequest to a dedicated library with the proper requirement.