Bug 1709893 - Part 2: Add missing nsPrintfCString.h include, r=ipc-reviewers,mccr8

Differential Revision: https://phabricator.services.mozilla.com/D114520

ipc/glue/ProcessUtils_common.cpp

@@ -9,6 +9,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/ipc/GeckoChildProcessHost.h"
 #include "mozilla/UniquePtrExtensions.h"
+#include "nsPrintfCString.h"
 
 namespace mozilla {
 namespace ipc {