Rename Brave Sync to Sync in settings

[btlechowski]

Follow up from #1183

Steps to Reproduce

1. Go to brave://settings
2. Scroll down to Brave Sync

Actual result:

The section is named Brave Sync

Expected result:

The section is named Sync

Brave version (brave://version info)

Brave	0.58.14 Chromium: 71.0.3578.98 (Official Build) (64-bit)
Revision	15234034d19b85dcd9a03b164ae89d04145d8368-refs/branch-heads/3578@{#897}
OS	Windows 7

@rebron @cezaraugusto @brave/legacy_qa

[LaurenWags]

Reproduces on macOS. Additionally, do we want to change the wording in the box from 'Access Brave Sync...' to 'Access Sync...'?

Brave	0.58.14 Chromium: 71.0.3578.98 (Official Build) (64-bit)
Revision	15234034d19b85dcd9a03b164ae89d04145d8368-refs/branch-heads/3578@{#897}
OS	Mac OS X

[cezaraugusto]

moving to 0.59 per last sync meeting

[darkdh]

If we rename this, we also need to rename the menu item

[btlechowski]

Reproduces on Ubuntu 17.10

Brave	0.58.14 Chromium: 71.0.3578.98 (Official Build) (64-bit)
Revision	15234034d19b85dcd9a03b164ae89d04145d8368-refs/branch-heads/3578@{#897}
OS	Linux

[GeetaSarvadnya]

Verification passed on

Brave	0.59.13 Chromium: 72.0.3626.28 (Official Build) beta (64-bit)
Revision	997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS	Windows

• Verified the STR mentioned in the issue.
  

Verification passed on

Brave 0.59.13 Chromium: 72.0.3626.28 (Official Build) beta (64-bit)
Revision 997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS Linux

• Verified the STR mentioned in the issue.
  
• Brave Sync is not renamed to Sync (Addressed in Brave sync is not renamed to Sync on Linux platform #2758)

Verified passed with

Brave	0.59.14 Chromium: 72.0.3626.28 (Official Build) beta(64-bit)
Revision	997b1040b63bac324e815797ba52be0cd8f616ed-refs/branch-heads/3626@{#461}
OS	Mac OS X