gnome-tweaks shouldn't require gnome-shell-extension-prefs

Impact
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There are now 2 apps in 22.04 LTS which allow configuring installed GNOME Shell Extensions:
- gnome-shell-extension-prefs -- built as part of gnome-shell (but in universe & not installed by default)
- gnome-shell-extension-manager -- this one additionally allows installing new extensions. Neither Firefox nor Chromium in Ubuntu have the Native Messaging Portal hooked up to allow chrome-gnome-shell to work. This makes gnome-shell-extension-manager the only GUI way in 22.04 LTS currently to install extensions from extensions.gnome.org.

GNOME Tweaks has a hard dependency on only the first app. The dependency was added years ago when Tweaks had a code dependency on the extensions app. The Tweaks app no longer has any features to manage installed Extensions. Therefore, I'm demoting this dependency to Suggests.

Also, this new version disables the notice on first run that extension management has moved to a different app. The notice has a link to
https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/HEAD/subprojects/extensions-app/README.md

which has a prominent Download on Flathub button which is unnecessary since the app is already in Ubuntu. There are 2 apps and the message only mentions one of them. Also, I believe the message is untranslated.

Test Case
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Install the new GNOME Tweaks version.
sudo apt remove gnome-shell-extension-prefs should work.

A new user shouldn't see a popup when they first start the Tweaks app.

You can replicate the new user experience by running
gsettings reset org.gnome.tweaks show-extensions-notice

What Could Go Wrong
--------------------
Users upgrading from Ubuntu 20.04 LTS won't be able to manage extensions unless they install one of the two extension apps. I will mention this in the Jammy Release Notes now.

Users who only had the one extension app because it was a hard dependency may have the app autoremoved.