Accessibility: Elastic UI Accordions

[aphelionz]

Subset of tickets in #614 that deal with the "Accordion" category of EUI, anything that falls on or under this URL: https://elastic.github.io/eui/#/layout/accordion

• "Increase Height" and "Decrease Height" buttons should provide context change information "Increase Height" and "Decrease Height" buttons should provide context change information #721
• Accordion Close button read as "Delete" by screen reader Accordion Close button read as "Delete" by screen reader #722

[myasonik]

Closing this meta ticket as it only tracks one issue