Change text version of warning mail to mention appeals instead of mails (#17725)

Also, the instruction to reply to e-mail would probably not work in many cases
where the notifications e-mail address is not able to receive incoming emails
or the mailbox is not actively monitored.

app/views/user_mailer/warning.text.erb

@@ -32,4 +32,5 @@
 ---
 <% end %>
 
-<%= t 'user_mailer.warning.get_in_touch', instance: @instance %>
+<%= t 'user_mailer.warning.appeal_description', instance: @instance %>
+<%= disputes_strike_url(@warning) %>