fix: translate unknown mod provider

Co-authored-by: flow <flowlnlnln@gmail.com>
Signed-off-by: leo78913 <leo3758@riseup.net>

launcher/minecraft/mod/Mod.cpp

@@ -202,5 +202,6 @@ auto Mod::provider() const -> QString
     if (metadata()) {
         return ProviderCaps.readableName(metadata()->provider);
     }
-    return "Unknown";
+	//: Unknown mod provider (i.e. not Modrinth, CurseForge, etc...)
+    return tr("Unknown");
 }