MINOR: Change “Choose Page” to “Search or choose Page” (#8766)

* MINOR: Change “Choose Page” to “Search or choose Page”

Based on discussions with James Ford, it wasn’t clear that you could
search.

* Use new translation key

lang/en.yml

@@ -48,7 +48,7 @@ en:
     VALIDDATETIMEMINDATE: 'Your date has to be newer or matching the minimum allowed date and time ({datetime})'
   SilverStripe\Forms\DropdownField:
     CHOOSE: (Choose)
-    CHOOSE_MODEL: '(Choose {name})'
+    SEARCH_OR_CHOOSE_MODEL: '(Search or choose {name})'
     SOURCE_VALIDATION: 'Please select a value within the list provided. {value} is not a valid option'
   SilverStripe\Forms\EmailField:
     VALIDATION: 'Please enter an email address'

src/Forms/TreeDropdownField.php

@@ -953,8 +953,8 @@ class TreeDropdownField extends FormField
 
         $item = DataObject::singleton($this->getSourceObject());
         $emptyString = _t(
-            'SilverStripe\\Forms\\DropdownField.CHOOSE_MODEL',
-            '(Choose {name})',
+            'SilverStripe\\Forms\\DropdownField.SEARCH_OR_CHOOSE_MODEL',
+            '(Search or choose {name})',
             ['name' => $item->i18n_singular_name()]
         );
         return $emptyString;