fix: typo for prop titles (jquense#2298)

Author: hydRAnger

stories/props/API.stories.mdx

@@ -823,7 +823,7 @@ Dates displayed in the gutter of the Agenda `view`
 
 Time only (not range) displayed in the gutter of the Agenda `view`
 
-## formats.agendaTimeRangeFormat
+### formats.agendaTimeRangeFormat
 
 - type: `function (range: Object {start: Date, end: Date}, culture: ?string, localizer: DateLocalizer) => string`
 - <LinkTo kind="props" story="formats-agenda-time-range-format">
@@ -832,7 +832,7 @@ Time only (not range) displayed in the gutter of the Agenda `view`
 
 Time range displayed in the gutter of the Agenda `view`
 
-# formats.eventTimeRangeFormat
+### formats.eventTimeRangeFormat
 
 - type: `function (range: Object {start: Date, end: Date}, culture: ?string, localizer: DateLocalizer) => string`
 - <LinkTo kind="props" story="formats-event-time-range-format">