Fix typo in headings and labels (#2411)

Author: daniel-montalvo

_rules/heading-descriptive-b49b2e.md

@@ -42,9 +42,9 @@ Headings that are visible but not in the accessibility tree are a failure of [Su
 
 ### Assumptions
 
-This rule assumes that the [flat tree][] order is close to the reading order as elements are rendered on the page. Due to positioning, it is possible to render a document in an order that greatly differs from the tree order, in which case the content which is visually associated with a heading might not be the content following it in tree order and this rule might fail while [Success Criterion 2.4.6 Headings and Label][sc246] is still satisfied.
+This rule assumes that the [flat tree][] order is close to the reading order as elements are rendered on the page. Due to positioning, it is possible to render a document in an order that greatly differs from the tree order, in which case the content which is visually associated with a heading might not be the content following it in tree order and this rule might fail while [Success Criterion 2.4.6 Headings and Labels][sc246] is still satisfied.
 
-This rule also assumes that the content the heading is intended to describe is [visible][] and not hidden from assistive technologies. Otherwise, cases such as expandable content using a heading might fail this rule while [Success Criterion 2.4.6 Headings and Label][sc246] is still satisfied.
+This rule also assumes that the content the heading is intended to describe is [visible][] and not hidden from assistive technologies. Otherwise, cases such as expandable content using a heading might fail this rule while [Success Criterion 2.4.6 Headings and Labels][sc246] is still satisfied.
 
 ### Accessibility Support