Remove muon / Brave (old) from importer

[LaurenWags]

Description

Per internal discussions, we decided to remove muon from the list of browsers to import from. It has been over a year since we did the migration from muon. Additionally, it is confusing to some users as they think they can import from other channels.

Test plan / Steps to Reproduce

1. Launch Brave
2. Go to brave://settings
3. Pick importer
4. Also can check from other places where import can be done (brave://welcome, etc)

Actual result:

Brave (old) is in the list to import from.

Expected result:

Brave (old) should not be in the list.

Reproduces how often:

easily

Brave version (brave://version info)

all

Version/Channel Information:

• Can you reproduce this issue with the current release? yes
• Can you reproduce this issue with the beta channel? yes
• Can you reproduce this issue with the dev channel? yes
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

at least one internal suggestion for this occurred here, but there were other discussions as well.
https://bravesoftware.slack.com/archives/C20HMJ62H/p1575914247322000
cc @bsclifton @rebron @brave/legacy_qa

[iefremov]

Thanks for filing this @LaurenWags !

[LaurenWags]

Verified passed with

Brave	1.8.71 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	macOS Version 10.14.6 (Build 18G3020)

• Verified test plan/STR from description
• Using 1.7.x, confirmed that with Brave muon installed/a muon profile present, you see Brave (old) in the importer drop down.

• Confirmed on 1.8.x with Brave muon installed, you do not see Brave (old) in the importer drop down.
• Confirmed on the following screens:
  • brave://welcome
  • Navigating to brave://settings/importData directly in URL bar
  • Navigating to brave://settings and then clicking on "Import bookmarks and settings" option, which opens brave://settings/importData
  • Navigating to hamburger menu > Bookmarks > Import Bookmarks and Settings, which opens brave://settings/importData
  • (macOS only) From macOS file menu opening Brave > Import Bookmarks and Settings..., which opens brave://settings/importData

• Confirmed other import options still displayed and functioned as expected. (Safari, Firefox, Chrome, Bookmarks HTML file)

Verification passed on

Brave	1.8.72 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	Ubuntu 18.04 LTS

• Verified test plan from description

• Confirmed on 1.8.x with Brave muon installed, you do not see Brave (old) in the importer drop down.

• Confirmed on the following screens:

  • brave://welcome
  • Navigating to brave://settings/importData directly in URL bar
  • Navigating to brave://settings and then clicking on "Import bookmarks and settings" option, which opens brave://settings/importData
  • Navigating to hamburger menu > Bo

Verification passed on

Brave	1.8.77 Chromium: 81.0.4044.92 (Official Build) dev (64-bit)
Revision	e98e6f21168a55e7ba57202f56323911cd9d31d1-refs/branch-heads/4044@{#883}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Confirmed on 1.8.x with Brave muon installed, you do not see Brave (old) in the importer drop down.
• Confirmed on the following screens:
  • brave://welcome
  • Navigating to brave://settings/importData directly in URL bar
  • Navigating to brave://settings and then clicking on "Import bookmarks and settings" option, which opens brave://settings/importData
  • Navigating to hamburger menu > Bookmarks > Import Bookmarks and Settings, which opens brave://settings/importData