Make figure and figcaption test just about figcaption
Make figure and figcaption test just about figcaption

…as there is already a figure test, which has tests for accessible
name/desc, etc. Make this just about figcaption mapping.

ThePacielloGroup/AT-browser-tests,ThePacielloGroup/AT-browser-tests,DHBrett/AT-browser-tests,DHBrett/AT-browser-tests