Status page: hush menu should be on top of other headers

[agh1]

Also tempered a bit of z-index overkill on the <li> elements in the menu

Overview

On statuses with short messages, the menu to hush the status for a week/month/forever overlaps the next status header. The menu should be on top of the header both for legibility and in order to click the last option.

Before

The next header is on top of the bottom of the menu. You cannot select the last option.

After

The menu is on top of the next header.

Technical Details

I set the z-index on the <ul> element. The constituent <li> elements had a z-index of 99999, which was excessive (it would appear on top of a modal, for example), so I dropped that down to 99 to allow some room for other things to go above it if necessary. These numbers aren't magical; I just want to avoid a z-index arms race.

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[mattwire]

@vingle Principal seems fine. Any thoughts?

[colemanw]

Looks good to me.

[vingle]

It worked for me (long time since I've seen a "font-size: smaller" property!)

[eileenmcnaughton]

test fails unrelated