Add T111 history to HACKING.rst

On the commit I36592a91001361d816e302745fe8417aee5e7565 , I forgot
to add T111 history to HACKING.rst. So this patch fixes it.

Change-Id: Ib4fd6e6d6f20cbe6c8b2914319aca721fb223850
diff --git a/HACKING.rst b/HACKING.rst
index 0962f80..efabaf6 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -18,6 +18,7 @@
 - [T109] Cannot use testtools.skip decorator; instead use
          decorators.skip_because from tempest-lib
 - [T110] Check that service client names of GET should be consistent
+- [T111] Check that service client names of DELETE should be consistent
 - [N322] Method's default argument shouldn't be mutable
 
 Test Data/Configuration