Remove last used message if key’s never been used

I don’t think it adds anything to tell you that a key’s never been used.
The value of the ‘key was used 3 minutes ago’ message is in stopping you
accidentally revoking something you shouldn’t have.

tests/app/main/views/test_templates.py

@@ -725,9 +725,7 @@ def test_should_show_delete_template_page_with_never_used_block(
         _test_page_title=False,
     )
     assert page.h1.text == 'Are you sure you want to delete Two week reminder?'
-    assert normalize_spaces(page.select('.banner-dangerous p')[0].text) == (
-        'It’s never been used.'
-    )
+    assert not page.select('.banner-dangerous p')
     assert normalize_spaces(page.select('.sms-message-wrapper')[0].text) == (
         'service one: Template <em>content</em> with & entity'
     )