Backport PR #2582: Fix displaying history when output cache is disabled.

Previously, disabling the output cache disabled all history. These were separated, but the `%hist` magic was left with an unnecessary check, where if the output cache was disabled, it would refuse to work.

Closes gh-2581

IPython/core/magics/history.py

@@ -98,10 +98,6 b' class HistoryMagics(Magics):'
 
         """
 
-        if not self.shell.displayhook.do_full_cache:
-            print('This feature is only available if numbered prompts '
-                  'are in use.')
-            return
         opts,args = self.parse_options(parameter_s,'noprtglf:',mode='string')
 
         # For brevity