Update dynarmic

Updated to incorporate fix from MerryMage/dynarmic#106 which is required
for using fmt in Citra.

externals/dynarmic

@@ -1 +1 @@
-Subproject commit 358cf7c32205a5114964865c86a8455daf810732
+Subproject commit 7707ff13e981b0aecf87f3156ee0b641469f7bb3