Disable safebrowsing download protection

[diracdeltas]

Safebrowsing download protection (not browsing protection) should be disabled until we find a way to prevent it from sending URLs to a remote service.

See https://feeding.cloud.geek.nz/posts/how-safe-browsing-works-in-firefox/ for instance

[diracdeltas]

Related: #4335 (for just Tor, not normal mode)

[diracdeltas]

cc @fmarier

[fmarier]

Test plan is the first part of what is mentioned in the PR:

To test that remote lookups are no longer done, go to https://testsafebrowsing.appspot.com and verify that none of the Download Warnings files get blocked.

The second part can't really be tested without making a custom build :(

[btlechowski]

@fmarier https://testsafebrosing.appspot.com/ gives me 404. The test plan needs to be updated.

[tildelowengrimm]

@btlechowski https://testsafebrowsing.appspot.com works fine for me.

[fmarier]

Sorry for the typo, I've fixed it in #4341 (comment).

[btlechowski]

Works now, I didn't notice the typo.

[btlechowski]

Verification passed on

Brave	0.72.112 Chromium: 78.0.3904.70 (Official Build) dev (64-bit)
Revision	edb9c9f3de0247fd912a77b7f6cae7447f6d3ad5-refs/branch-heads/3904@{#800}
OS	Ubuntu 18.04 LTS

Verified test plan based on #4341 (comment)

Verification passed on

Brave	1.1.1 Chromium: 78.0.3904.97 (Official Build) beta (64-bit)
Revision	021b9028c246d820be17a10e5b393ee90f41375e-refs/branch-heads/3904@{#859}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

Verified test plan based on #4341 (comment)

Verified passed with

Brave	1.1.5 Chromium: 78.0.3904.97 (Official Build) beta (64-bit)
Revision	021b9028c246d820be17a10e5b393ee90f41375e-refs/branch-heads/3904@{#859}
OS	macOS Version 10.13.6 (Build 17G5019)

• Verified first part of test plan from Disable download protection remote lookups (brave/brave-browser#4341) brave-core#2710 per Disable safebrowsing download protection  #4341 (comment).
• Confirmed via LittleSnitch that while downloading the items from https://testsafebrowsing.appspot.com no calls were made to sb-ssl.google.com or sb-ssl.brave.com. All items downloaded successfully.