Changing delete channel modal text (#4348)

* Change Native Download Link Copy

* Change Native Download Apps Link Copy

* Update delete_channel_modal.jsx

Modified delete channel modal confirmation text to make it more impactful.

* Update en.json

Updated delete channel modal text to make it more impactful.

webapp/components/delete_channel_modal.jsx

@@ -71,7 +71,7 @@ export default class DeleteChannelModal extends React.Component {
                 <Modal.Body>
                     <FormattedMessage
                         id='delete_channel.question'
-                        defaultMessage='Are you sure you wish to delete the {display_name} {term}?'
+                        defaultMessage='This will delete the channel from the team and make its contents inaccessible for all users. Are you sure you wish to delete the {display_name} {term}?'
                         values={{
                             display_name: this.props.channel.display_name,
                             term: (channelTerm)