convert or remove existing instances of aria-alert=true

fixes CNVS-25676

test plan:
** Help dialog:
- Navigate to the help menu.
- Select the 'Report a Problem' menu item.
- The text block beginning with the text: "For an instant answer" should
  receive screenreader priority / focus.

** No Outcomes Warning
- I cannot get this to render via the UI; I may actually just remove it.

** Outcomes template
- Navigate to the Oucomes tab for a course with an outcome (or create one).
- Click on the name of the outcome in the left hand tab so that the
  information is displayed in the content view on the right side.
- Observe that there is a screenreader only element 'displaying' the
  title. (I opted not to update this to be a role="alert", as it didn't
  seem like the correct usage of this attribute. Happy to be told
  otherwise.

** Select content dialog
- Be logged in as an instructor.
- Navigate to the assignments page, then click on the `+` to create a
  new assignment.
- On the new assignment page, go the `Submission Type` select box, and
  select `External Tool`.
- Click on the `Find` button. This will open the `Configure External
  Tool` dialog.
- Observe that the follow text receives focus: `Select a tool from the
  list below, or enter a URL for an external tool you already know is
  configured with Basic LTI to add a link to it to this module.`

Change-Id: If4868654778b6933ff4aeb55de20190f2d909ecd
Reviewed-on: https://gerrit.instructure.com/76707
Tested-by: Jenkins
Reviewed-by: Matt Berns <mberns@instructure.com>
QA-Review: Indira Pai <ipai@instructure.com>
Product-Review: Nathan Rogowski <nathan@instructure.com>

Author: John Corrigan

app/views/jst/helpDialog.handlebars

@@ -24,7 +24,7 @@
   </form>
   <form class="help-dialog-pane bootstrap-form" id="create_ticket" style="display:none" action="/error_reports" method="POST">
     <h4>{{#t "file_a_ticket_for_a_personal_response_from_our_support_team"}}File a ticket for a personal response from our support team{{/t}}</h4>
-    <div aria-alert="true" class="alert">
+    <div role="alert" class="alert">
       <strong>{{#t "for_an_instant_answer"}}For an instant answer:{{/t}}</strong>
       <div>{{#t "see_if_your_issue_is_addressed_in_the_canvas_guides"}}See if your issue is addressed in the <a target="_blank" href="http://guides.canvaslms.com/">Canvas Guides</a>.{{/t}}</div>
     </div>

app/views/jst/outcomes/noOutcomesWarning.handlebars

@@ -1,5 +1,5 @@
 <div class="no-outcomes-warning">
-  <div class="alert" aria-live="true" aria-alert="true">
+  <div class="alert" role="alert">
     {{#t}}You have no outcomes. <a href="{{addOutcomesUrl}}" aria-label="{{noOutcomesLinkLabel}}">Click here</a> to create one.{{/t}}
   </div>
 </div>

app/views/jst/outcomes/outcome.handlebars

@@ -1,4 +1,4 @@
-<h2 class="screenreader-outcome-title screenreader-only" tabindex="0" aria-alert="true">
+<h2 class="screenreader-outcome-title screenreader-only" tabindex="0">
   {{title}}
 </h2>
 <h2 class="title" role="presentation">

app/views/shared/_select_content_dialog.html.erb

@@ -79,7 +79,7 @@
       <% end %>
       <% if !only || only.include?(:external_tools) %>
       <div id="context_external_tools_select" class="module_item_option">
-        <div style="font-size: 0.8em;" tabindex="0" aria-alert="true">
+        <div style="font-size: 0.8em;" tabindex="0" role="alert">
           <i class="icon-link"></i>
           <%= t :external_tool_notice, "Select a tool from the list below, or enter a URL for an external tool you already know is configured with Basic LTI to add a link to it to this *module*.", :wrapper => '<span class="holder_type">\1</span>' %>
         </div>