lost pinned top sites on NTP upon upgrade

[rebron]

Description

Using 1.8.25 and upgrading via download/install of 1.8.28 (but likely in 1.8.27 also), 3 pinned tabs disappear upon relaunch. Expectation is that those pinned tabs and all tabs remain the same after upgrading. Subsequent attempts to reload or open new brave://newtab don't bring them back.

Test plan / Steps to Reproduce

1. Older profile. Pin 2 or 3 top sites on the New Tab Page brave://newtab
2. Download 1.8.27 or 1.8.28
3. Notice that the pinned top tiles are missing.

Actual result:

Expected result:

Reproduces how often:

Might be difficult to reproduce.

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release? No
• Can you reproduce this issue with the beta channel? No
• Can you reproduce this issue with the dev channel? No
• Can you reproduce this issue with the nightly channel? 1.8.27 and higher

Miscellaneous Information:

[GeetaSarvadnya]

Verification passed on

Brave	1.8.79 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)

• Verified the STR from the description
• Logged a follow-up issue Follow up of #8781 - Pinned sites are being duplicated after upgrade #9299

Verified passed with

Brave	1.8.82 Chromium: 81.0.4044.113 (Official Build) dev (64-bit)
Revision	e3225dafb0475864a1812a374d73a92e391635ac-refs/branch-heads/4044@{#936}
OS	macOS Version 10.14.6 (Build 18G3020)

• Verified STR from description

Verification passed on

Brave	1.8.82 Chromium: 81.0.4044.113 (Official Build) dev (64-bit)
Revision	e3225dafb0475864a1812a374d73a92e391635ac-refs/branch-heads/4044@{#936}
OS	Ubuntu 18.04 LTS

Verified test plan from the description