OIG - move background color to oig-logo instead of its parent

[rfultz]

Summary

• Resolves #6178
• Resolves #6213

Changing style rules for the logo/content block on the OIG page. Removed the background color and padding from the block so the content can set its own, though also moved those rules to the placeholder-oig-logo class

Required reviewers

-UX

Impacted areas of the application

Only the OIG landing page, the logo/content block and the submit button

Screenshots

Related PRs

None

How to test

• check the screenshot …
• merge
• deploy
• publish my saved draft of the OIG page

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.00%. Comparing base (cf19bed) to head (f0bbd1e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #6281 +/- ## ======================================== Coverage 78.00% 78.00% ======================================== Files 291 291 Lines 9414 9414 Branches 681 681 ======================================== Hits 7343 7343 Misses 2071 2071 ```

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