Revert features to correct state after disabling field trials

[jumde]

Description

Follow-up issue to #4283

• EV status should be set to lock instead of secure chip
• Remove features from brave_main_delegate.cc that were enabled/disabled because of field trials
• Set kExtensionsInstallVerification to enforce-strict for BravePDFDownloadTest.VerifyChromiumPDFExntension

Test Plan

Specified here: brave/brave-core#2471

[btlechowski]

Verification passed on

Brave	0.68.109 Chromium: 76.0.3809.62 (Official Build) dev (64-bit)
Revision	7b77856b3aa34d72f246d12340fc1ded8b2c0e83-refs/branch-heads/3809@{#798}
OS	Ubuntu 18.04 LTS

Verified test plan from brave/brave-core#2471

Only Lock is displayed

Verification passed on

Brave	0.68.114 Chromium: 76.0.3809.87 (Official Build) beta (64-bit)
Revision	111fe1e15d5ced26080a7dc239bcfe70f6c49aad-refs/branch-heads/3809@{#967}
OS	Windows 10 OS Version 1803 (Build 17134.523)

• Verified test plan from Issue 4552: Restore features to correct state after disabling field trials brave-core#2471

Verified passed with

Brave	0.68.114 Chromium: 76.0.3809.87 (Official Build) beta (64-bit)
Revision	111fe1e15d5ced26080a7dc239bcfe70f6c49aad-refs/branch-heads/3809@{#967}
OS	Mac OS X

• Verified test plan from Issue 4552: Restore features to correct state after disabling field trials brave-core#2471