fix: Wizard step 3 and 5 enhanced accordingly (fossasia#5365)

Author: terminator0309

app/components/forms/wizard/custom-form-input.hbs

@@ -1,10 +1,10 @@
 <div class="ui hidden divider"></div>
-<h3 class="ui dividing header">
+<div class="ui dividing">
   <i class="checkmark box icon"></i>
-  <div class="content">
+  <span class="content">
     {{t 'Add Custom Form Field'}}
-  </div>
-</h3>
+  </span>
+</div>
 <div {{did-update this.updated @field}} class="ui action input" style="width: inherit;">
   <Input type="text" placeholder="Field Name" @value={{this.name}} />
   <UiDropdown class="ui selection dropdown" @selected={{this.type}} @onChange={{action (mut this.type)}}>

app/templates/components/forms/wizard/sessions-speakers-step.hbs

@@ -190,7 +190,7 @@
     <h3 class="ui dividing header">
       <i class="checkmark box icon"></i>
       <div class="content">
-        {{t 'Customize registration form'}}
+        {{t 'Customize submission forms'}}
       </div>
     </h3>