Remove the chrome repository erroneously added by brave-browser on Linux

[fmarier]

As a follow-up to #1084, we should clean up existing installations that have had the Google repo added automatically by the cronjob.

Files to delete (if they exist):

• /etc/default/brave-browser
• /etc/apt/sources.list.d/brave-browser.list or /etc/yum.repos.d/brave-browser.repo

And then there's the Google repository signing key. For that, we need to first check whether or not chrome is installed on the machine. To do this, we could look for one of these files:

• /etc/cron.daily/google-chrome
• /etc/default/google-chrome
• /etc/apt/sources.list.d/google-chrome.list or /etc/yum.repos.d/google-chrome.repo

or their equivalents for beta:

• /etc/cron.daily/google-chrome-beta
• /etc/default/google-chrome-beta
• /etc/yum.repos.d/google-chrome-beta.repo

or dev:

• /etc/cron.daily/google-chrome-unstable
• /etc/default/google-chrome-unstable
• /etc/yum.repos.d/google-chrome-unstable.repo-

If there are no traces of Chrome, then we can remove the Google package signing key:

apt-key del D38B4796

or

rpm -e gpg-pubkey-7fac5991-4615767f
rpm -e gpg-pubkey-d38b4796-570c8cd3

[fmarier]

Note: the google-chrome packages don't remove their signing keys when the packages are apt purged.

[fmarier]

I have a fix for this in https://github.com/fmarier/brave-core/tree/issue2927, but I would prefer to see brave/brave-core#1078 land separately first so that we can confirm that the repo isn't added anymore, before we delete it.

[rebron]

@fmarier QA needed?

[srirambv]

Verification passed on

Brave	0.63.46 Chromium: 74.0.3729.91 (Official Build) (64-bit)
Revision	03844ed83e02b8add3f4b9cb859a7108d55b2e4d-refs/branch-heads/3729@{#860}
OS	Linux

• Verified installing 0.58.16 added brave-browser.list file in etc/apt/sources.list.d/
• Verified upgrading to current release build via apt created brave-browser-release-bionic.list file along with brave-browser.list
• Verified upgrading to 0.63.46 removed brave-browser.list file from etc/apt/sources.list.d/