manifest: Remove platform/platform_testing

Save disk space.

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: Icf0bb34a39321fcfce12245b4e64bc702cea0051

remove.xml

@@ -128,6 +128,8 @@
   <remove-project name="platform/packages/services/Telecomm" />
   <remove-project name="platform/packages/services/Telephony" />
 
+  <remove-project name="platform/platform_testing" />
+
   <remove-project name="platform/system/core" />
   <remove-project name="platform/system/extras" />
   <remove-project name="platform/system/media" />