Update Rust crate pem to v3

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
pem (source)	dependencies	major	2 -> 3

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Release Notes

jcreekmore/pem-rs (pem)

### [`v3.0.0`](https://togithub.com/jcreekmore/pem-rs/blob/HEAD/CHANGELOG.md#300) [Compare Source](https://togithub.com/jcreekmore/pem-rs/compare/v2.0.1...v3.0.0) - trim `proptest` features to prevent an MSRV break for testing - make EncodeConfig struct extendable and add a line_wrap config option ### [`v2.0.1`](https://togithub.com/jcreekmore/pem-rs/blob/HEAD/CHANGELOG.md#201) [Compare Source](https://togithub.com/jcreekmore/pem-rs/compare/v2.0.0...v2.0.1) - Fix serde support on no_std - Drop MSRV to 1.60

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