sync still shows as an option in settings

[rebron]

Test plan

1. Fresh install
2. Visit brave://settings
3. Verify Sync doesn't show up on side menu or in main settings area
4. Visit brave://flags/#brave-sync
5. Enable the setting and restart the browser
6. Visit brave://settings
7. Verify Sync DOES show up on side menu and in main settings area

Description

Temporarily disabling sync in 1.3.115 still shows Sync menu item in preferences. Sync menu item should be gone or displayed as disabled. Sync section for setting is removed however.

Actual result:

Expected result:

Sync menu item should be removed or showed as disabled.

[kjozwiak]

Removing this from https://github.com/brave/brave-browser/milestone/79 as per earlier conversations. This will be addressed in another release if we decide to remove the Sync menu item from brave://settings. CCing @rebron

[GeetaSarvadnya]

Verification passed on

Brave	1.3.116 Chromium: 80.0.3987.106 (Official Build) (64-bit)
Revision	f68069574609230cf9b635cd784cfb1bf81bb53a-refs/branch-heads/3987@{#882}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• Verified the STR from the description
• Verified that by default Sync doesn't show up in the side menu in brave://settings
  
• Verified that by default sync option doesn't show up in the hamburger menu in Normal, PT and TOR tabs.
• Verified that Sync is disabled by default and it can be enabled via brave://flags/#brave-sync
• Verified that Sync option is shown in the hamburger menu in Normal, PT and TOR tabs when sync is enabled via brave://flags/#brave-sync
• Verified that Sync should show up in the side menu in brave://settings when sync is enabled via brave://flags/#brave-sync
• Additional testing is covered in Flag to re-enable sync #8187 (comment)

---

Verification passed on

Brave	1.3.116 Chromium: 80.0.3987.106 (Official Build) (64-bit)
Revision	f68069574609230cf9b635cd784cfb1bf81bb53a-refs/branch-heads/3987@{#882}
OS	Linux

• Verified Sync is not shown in settings side bar when flag is not enabled
  
• Verified sync option is not shown on menu for Normal/Private/Tor windows
• Verified visiting brave://sync loads an error page when flag is disabled
• Verified sync option is shown in settings side bar when brave://flags#brave-sync is enabled
  
• Verified after enabling flag, Sync option is shown on all Normal/Private/Tor Windows and selecting it from the menu opens a sync page on normal tab window
• Verified brave://sync opens up sync start page when flag is enabled

Verified passed with

Brave	1.3.116 Chromium: 80.0.3987.106 (Official Build) (64-bit)
Revision	f68069574609230cf9b635cd784cfb1bf81bb53a-refs/branch-heads/3987@{#882}
OS	macOS Version 10.14.6 (Build 18G3020)

• Verified the STR from the description

- Verified enabling the flag does display Sync on brave://settings: