Recently viewed is not accessible in screenreader

[bhavyarm]

Kibana version: 6.3.0 BC3

Elasticsearch version: 6.3.0 BC3

Server OS version: darwin_x86_64

Browser version: chrome latest

Browser OS version: OS X

Original install method (e.g. download page, yum, from source, etc.): from staging

Describe the bug:
Recently viewed text on Kibana home is not keyboard or screenreader accessible. Without it being accessible - users don't have the context to which section of Kibana home page they are on.

Steps to reproduce:

1. Use either voiceover or chromevox - they won't announce that user is in recently viewed section
2. You can tab through the links though and they get announced.

Expected behavior: Recently viewed needs to be screenreader accessible.

[bhavyarm]

cc @nreese

[bhavyarm]

Spoke to CJ about it - not everything needs to be keyboard accessible. and he says it needs be a heading instead of a paragraph.