build(deps): minimize out-of-the-box dependencies

[0x676e67]

close: #901

[Copilot]

Pull Request Overview

This PR reduces the default dependencies by removing charset and system-proxy from the default feature set, keeping only webpki-roots enabled by default. This change minimizes out-of-the-box dependencies while still maintaining essential TLS certificate functionality.

• Removed charset and system-proxy from default features in Cargo.toml
• Updated documentation to reflect that these features are no longer enabled by default

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Cargo.toml	Removes charset and system-proxy from the default feature list
src/lib.rs	Updates feature documentation to remove "enabled by default" annotations for affected features

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