Admin Search Result Table Minor Styling Fix.

[ianliuwk1019]

Describe the Bug
Due to the low contrast, this is not easy to notice.
The search result table seems to have some white rectangle box looking not properly aligned with the content inside and around.

Probably better just try to remove extra white rectangle box styling.

** Steps To Reproduce**
Steps to reproduce the behaviour:

1. Go to FOM "Admin" frontend.
2. Search in general.
3. Verify the search result table.

Screenshots

Additional context
Add any other context about the problem here.