"Brave Ads has arrived!" notification should be shown on Linux after upgrade from 0.62.x

[tmancey]

Description

"Brave Ads has arrived!" notification should be shown on Linux after upgrade from 0.62.x

Steps to Reproduce

1. Install 0.62.x
2. Upgrade to 0.63.x or above

Actual result:

"Brave Ads has arrived!" notification was not shown on Linux after upgrading from 0.62.x

Expected result:

"Brave Ads has arrived!" notification should be shown on Linux after upgrading from 0.62.x

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

0.63.x, 0.64.x, 0.65.x and 0.66.x

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• Can you reproduce this issue with the beta channel? Yes
• Can you reproduce this issue with the dev channel? Yes
• Can you reproduce this issue with the nightly channel? Yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? NO
• Does the issue resolve itself when disabling Brave Rewards? NO
• Is the issue reproducible on the latest version of Chrome? N/A

Miscellaneous Information:

brave_ads_enabled (https://github.com/brave/brave-core/blob/0.62.x/components/brave_ads/browser/buildflags/buildflags.gni) was set to false on Linux for 0.62.x

brave_ads_enabled (https://github.com/brave/brave-core/blob/0.63.x/components/brave_ads/browser/buildflags/buildflags.gni) was set to true for Linux on 0.63.x

And the upgrade path assumed this value would always be true for all platforms when migrating.

[srirambv]

Verification passed on

Brave	0.64.75 Chromium: 74.0.3729.131 (Official Build) (64-bit)
Revision	518a41c1fa7ce1c8bb5e22346e82e42b4d76a96f-refs/branch-heads/3729@{#954}
OS	Linux

• Verified installing 0.62.51 and enabling rewards and upgrading to 0.64.75 shows ads is available notification