doc: update rule-descriptions (#1035)
doc: update rule-descriptions (#1035)

This patch updates the `rule-descriptions.md` document via `npx grunt build`. It appears the source files in which this document have changed but the generated content has not been comitted.

I've been "ignoring" this change in the many PRs I've opened recently and have finally grown tired of doing so.


## Reviewer checks

**Required fields, to be filled out by PR reviewer(s)**
- [x] Follows the commit message policy, appropriate for next version
- [x] Has documentation updated, a DU ticket, or requires no documentation change
- [x] Includes new tests, or was unnecessary
- [x] Code is reviewed for security by: Marcy Sutton
dequelabs/axe-core,dequelabs/axe-core,dequelabs/axe-core,dequelabs/axe-core