Fix h4 passes to BillBoard headingAs prop

flag=none

Test Plan:
 - specs pass

Change-Id: If0b5b243282dc39090931ff09c0f55c09b9fa4df
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/277564
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Omar Soto-Fortuño <omar.soto@instructure.com>
QA-Review: Omar Soto-Fortuño <omar.soto@instructure.com>
Product-Review: Omar Soto-Fortuño <omar.soto@instructure.com>

jest/jest-setup.js

@@ -63,7 +63,6 @@ const ignoredErrors = [
   /Invalid prop `editorOptions.plugins` of type `string` supplied to `(ForwardRef|RCEWrapper)`/, // https://instructure.atlassian.net/browse/MAT-453
   /Invalid prop `editorOptions.toolbar\[0\]` of type `string` supplied to `(ForwardRef|RCEWrapper)`/, // https://instructure.atlassian.net/browse/MAT-453
   /Invalid prop `heading` of type `object` supplied to `Billboard`/, // https://instructure.atlassian.net/browse/QUIZ-8870
-  /Invalid prop `headingAs` of value `h4` supplied to `Billboard`/,
   /Invalid prop `returnFocusTo` of type `DeprecatedComponent` supplied to `(CourseHomeDialog|HomePagePromptContainer)`/,
   /Invalid prop `selectedDate` of type `date` supplied to `CanvasDateInput`/,
   /Invalid prop `value` of type `object` supplied to `CanvasSelect`/,

ui/features/assignments_show_student/react/components/AttemptType/UrlEntry.js

@@ -207,7 +207,7 @@ class UrlEntry extends React.Component {
     <View as="div" borderWidth="small" data-testid="url-entry" margin="0 0 medium 0">
       <Billboard
         heading={I18n.t('Enter Web URL')}
-        headingAs="h4"
+        headingAs="span"
         headingLevel="h4"
         message={this.renderURLInput()}
         theme={{backgroundColor: theme.variables.colors.porcelain}}