Show Japanese GC games in Japanese when using TitleDatabase

Because the GC language setting cannot be set to Japanese, we
need a special condition for Japanese GC games. I accidentally
removed it in PR 7816, but here it is again in a new form.

We could do the same thing with Korean GC games if we want to
(which we couldn't do before PR 7816), but due to how spotty
GameTDB is with having Korean names for Korean GC releases,
things will be more consistent if we just use English for them.

Source/Core/UICommon/GameFile.cpp

@@ -60,6 +60,9 @@ static bool UseGameCovers()
 
 DiscIO::Language GameFile::GetConfigLanguage() const
 {
+  if (m_platform == DiscIO::Platform::GameCubeDisc && m_country == DiscIO::Country::Japan)
+    return DiscIO::Language::Japanese;
+
 #ifdef ANDROID
   // TODO: Make the Android app load the config at app start instead of emulation start
   // so that we can access the user's preference here