MDL-87757 block_myoverview: Remove navigation role and behat update

- Removal of the navigation role on main and zero-state template
- Add accessibility extra tests for the block_overview

public/blocks/myoverview/templates/main.mustache

@@ -23,7 +23,7 @@
     {}
 }}
 
-<div id="block-myoverview-{{uniqid}}" class="block-myoverview block-cards" data-region="myoverview" role="navigation">
+<div id="block-myoverview-{{uniqid}}" class="block-myoverview block-cards" data-region="myoverview">
     <div role="search" data-region="filter" class="d-flex align-items-center my-2" aria-label="{{#str}} aria:controls, block_myoverview {{/str}}">
         <div class="d-flex flex-wrap gap-1 align-items-center w-100">
             {{> block_myoverview/nav-grouping-selector }}

public/blocks/myoverview/templates/zero-state.mustache

@@ -44,7 +44,7 @@
     }
 }}
 
-<div class="block-myoverview block-cards" data-region="myoverview" role="navigation">
+<div class="block-myoverview block-cards" data-region="myoverview">
     <div class="container-fluid p-0">
         <div class="text-xs-center text-center mt-3" data-region="empty-message">
             <img class="empty-placeholder-image-lg mt-1"

public/blocks/myoverview/tests/behat/block_myoverview_dashboard.feature

@@ -322,6 +322,6 @@ Feature: The my overview block allows users to easily access their courses
     Then I should not see "Category 1" in the "Course overview" "block"
 
   @accessibility
-  Scenario: The dashboard page must have sufficient colour contrast
+  Scenario: The My courses page must meet accessibility standards
     When I am on the "My courses" page logged in as "student1"
-    Then the page should meet "wcag143" accessibility standards
+    Then the page should meet accessibility standards with "best-practice" extra tests

public/blocks/myoverview/tests/behat/block_myoverview_zerostate.feature

@@ -88,4 +88,4 @@ Feature: Zero state on my overview block
   @javascript @accessibility
   Scenario: Evaluate the accessibility of the My courses (zero state)
     When I am on the "My courses" page logged in as "manager"
-    Then the page should meet accessibility standards
+    Then the page should meet accessibility standards with "best-practice" extra tests