no notification after successful tip - follow up to 2114

[LaurenWags]

Description

Per test plan for #2114 (in PR brave/brave-core#896), there should be a notification after a tip is successful. No notification is being shown after successful tip.

Steps to Reproduce

1. Clean profile on 0.57.8
2. Enable Rewards
3. Accept UGP grant.
4. Tip a site (or YT channel)

Actual result:

No notification shown on BAT logo or when you view Brave Rewards Panel from logo.

Expected result:

Notification should be displayed and should show correct tip amount.

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.57.8 Chromium: 71.0.3578.53 (Official Build) beta(64-bit)
Revision	599fb72e740eab9d10609f1ed28a2ad669f82c1a-refs/branch-heads/3578@{#669}
OS	Mac OS X

Reproducible on current release:

• Does it reproduce on brave-browser dev/beta builds? yes

Website problems only:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Additional Information

Reproduced by @btlechowski
cc @brave/legacy_qa for verification on other platforms

[LaurenWags]

cc @rebron @NejcZdovc as the original issue 2114 was slated for 0.57.x

[NejcZdovc]

this was changed and now we only show notification for auto contribute. Closing as there is no plan to add it for tip