Update Ruby dependencies to address nokogiri issue

[jkmassel]

Nokogiri v1.16.5 upgrades its dependency libxml2 to 2.12.7 from 2.12.6.

libxml2 v2.12.7 addresses CVE-2024-34459:

described at https://gitlab.gnome.org/GNOME/libxml2/-/issues/720
patched by https://gitlab.gnome.org/GNOME/libxml2/-/commit/2876ac53

Fixes https://github.com/wordpress-mobile/WordPress-iOS/security/dependabot/27

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr23461-666b15e
	Version	25.2
	Bundle ID	com.jetpack.alpha
	Commit	666b15e
	App Center Build	jetpack-installable-builds #9447

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr23461-666b15e
	Version	25.2
	Bundle ID	org.wordpress.alpha
	Commit	666b15e
	App Center Build	WPiOS - One-Offs #10405

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[AliSoftware]

Looking good 👍

💡 💭 @jkmassel You might want to apply a similar update on WordPressAuthenticator-iOS while at it.

I noticed there was a quite old PR created by dependabot for numping nokogiri on that repo already, but it's quite outdated and for an even older version; not sure why dependabot wasn't able to auto-create a PR for this alert in that other repo 🤷