Update banner to fit width of the screen (#1635)
Update banner to fit width of the screen (#1635)

Summary:
# Problem
The banner's font size as well as other styles are not adjusting to the screen.
This is because of the wrong style in media.

# Code
Should be `div[class^="announcementBarContent"]` instead of `.announcement` as the actual banner content class is `.announcementBarContent_6uhP.`

# Screenshots
![Screenshots](https://user-images.githubusercontent.com/78584173/166882195-43d0db18-b9d4-43be-82fc-10a4ccaba481.png)

Pull Request resolved: https://github.com/facebook/infer/pull/1635

Reviewed By: skcho

Differential Revision: D37714878

Pulled By: jvillard

fbshipit-source-id: 2ba3887b32c2054712712727d9eb87674a9ae16b

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