Bug 1227347, part 1 - Remove IPC-related LSan suppressions. r=erahm

It seems like these were fixed by making graphics IPC shut down
properly.

build/sanitizers/lsan_suppressions.txt

@@ -76,12 +76,6 @@ leak:processInternalEntity
 # Bug 1187421 - With e10s, NSS does not always free the error stack. m1.
 leak:nss_ClearErrorStack
 
-# Bug 1122045 - Leaks in MessageLoop::MessageLoop()
-leak:MessageLoop::MessageLoop
-# This may not actually be related to MessageLoop.
-leak:base::WaitableEvent::TimedWait
-leak:MessageLoop::PostTask_Helper
-
 # Bug 1189430 - DNS leaks in mochitest-chrome.
 leak:nsDNSService::AsyncResolveExtended
 leak:_GetAddrInfo_Portable