Stop terminating shackle pools on buoy app stop

buoy_app:stop/1 called shackle_pool:terminate(), which deletes the
shackle_pool foil namespace while the shackle application is still
running. shackle only rebuilds that namespace when its own supervisor
starts, so any shackle_pool:start after a buoy restart in the same VM
silently lost its foil entries and every request failed with
pool_not_started. shackle_app:stop/1 already performs this cleanup
when shackle itself stops.

Author: lpgauth

src/buoy_app.erl

@@ -36,5 +36,4 @@ start(_StartType, _StartArgs) ->
     ok.
 
 stop(_State) ->
-    shackle_pool:terminate(),
     ok.