Bug 1634658 - Make AudioIPC nightly-only for 32-bit Windows. r=chunmin

Differential Revision: https://phabricator.services.mozilla.com/D73429

modules/libpref/init/StaticPrefList.yaml

@@ -6350,6 +6350,8 @@
   mirror: always
 #if defined(XP_LINUX) && !defined(MOZ_WIDGET_ANDROID)
   value: true
+#elif defined(XP_WIN) && defined(_X86_)
+  value: @IS_NIGHTLY_BUILD@
 #elif defined(XP_WIN) && !defined(_ARM64_)
   value: true
 #else