[Ubuntu] Use mozilla official apt repo for installing firefox

[TerrorJack]

The mozillateam ppa contains outdated firefox version. Mozilla has an official apt repo that provides up-to-date firefox package in sync with other OTA release channels, so use that instead.

Description

New tool, Bug fixing, or Improvement?
Please include a summary of the change and which issue is fixed. Also include relevant motivation and context.
For new tools, please provide total size and installation time.

Related issue:

Check list

• Related issue / work item is attached
• Tests are written (if applicable)
• Documentation is updated (if applicable)
• Changes are tested and related VM images are successfully generated

[janbrasna]

I'm only wondering whether the GPG fingerprint shouldn't be checked, too?

[janbrasna]

(Note this needs a rebase / conflicts resolved.)

This may also need entries in 3rdparty sources updated:

runner-images/README.md

Lines 124 to 133 in 95dda62

	### Package managers usage
	We use third-party package managers to install software during the image generation process. The table below lists the package managers and the software installed.
	> [!NOTE]
	> Third-party repositories are re-evaluated every year to identify if they are still useful and secure.
	| Operating system | Package manager | Third-party repos and packages |
	| :--- | :---: | ---: |
	| Ubuntu | [APT](https://wiki.debian.org/Apt) | [docker](https://download.docker.com/linux/ubuntu) <br/> [Eclipse-Temurin (Adoptium)](https://packages.adoptium.net/artifactory/deb/) <br/> [Erlang](https://packages.erlang-solutions.com/ubuntu) <br/> [Firefox](https://ppa.launchpad.net/mozillateam/ppa/ubuntu) <br/> [git-lfs](https://packagecloud.io/install/repositories/github/git-lfs) <br/> [git](https://launchpad.net/~git-core/+archive/ubuntu/ppa) <br/> [Google Cloud CLI](https://packages.cloud.google.com/apt) <br/> [Heroku](https://cli-assets.heroku.com/channels/stable/apt) <br/> [HHvm](https://dl.hhvm.com/ubuntu) <br/> [MongoDB](https://repo.mongodb.org/apt/ubuntu) <br/> [Mono](https://download.mono-project.com/repo/ubuntu) <br/> [MS Edge](https://packages.microsoft.com/repos/edge) <br/> [PostgreSQL](https://apt.postgresql.org/pub/repos/apt/) <br/> [R](https://cloud.r-project.org/bin/linux/ubuntu) |
	| | [pipx](https://pypa.github.io/pipx) | ansible-core <br/>yamllint |