MDL-52964 Qtype: Small fixes to behat tests

This applies some small changes to proposed behat tests:

- Geting rid of the @javascript tag when it's not needed.
- Adding some missing @_switch_window tags.
- Fixing some scenario names, previously duplicated.
- Fixing some typos and whitespace.

question/type/description/tests/behat/add.feature

@@ -18,7 +18,6 @@ Feature: Test creating a Description question
     And I follow "Course 1"
     And I navigate to "Question bank" node in "Course administration"
 
-  @javascript
   Scenario: Create a Description question with Correct answer as False
     When I add a "Description" question filling the form with:
       | Question name                      | description-001                                                |

question/type/description/tests/behat/edit.feature

@@ -24,7 +24,6 @@ Feature: Test editing a Description question
     And I follow "Course 1"
     And I navigate to "Question bank" node in "Course administration"
 
-  @javascript
   Scenario: Edit a Description question
     When I click on "Edit" "link" in the "description-001" "table_row"
     And I set the following fields to these values:

question/type/description/tests/behat/export.feature

@@ -23,7 +23,6 @@ Feature: Test exporting Description questions
     And I log in as "teacher1"
     And I follow "Course 1"
 
-  @javascript
   Scenario: Export a Description question
     When I navigate to "Export" node in "Course administration > Question bank"
     And I set the field "id_format_xml" to "1"

question/type/description/tests/behat/preview.feature

@@ -24,8 +24,8 @@ Feature: Preview a Description question
     And I follow "Course 1"
     And I navigate to "Question bank" node in "Course administration"
 
-  @javascript
-  Scenario: Preview a question and submit a correct response.
+  @javascript @_switch_window
+  Scenario: Preview a Description question and submit a correct response.
     When I click on "Preview" "link" in the "description-001" "table_row"
     And I switch to "questionpreview" window
     And I set the field "How questions behave" to "Immediate feedback"