chore: add back deprecation warnings and disable all API deprecated before 6.0

Signed-off-by: Trial97 <alexandru.tripon97@gmail.com>

launcher/modplatform/legacy_ftb/PackFetchTask.cpp

@@ -79,7 +79,7 @@ void PackFetchTask::fetchPrivate(const QStringList& toFetch)
         QObject::connect(job, &NetJob::succeeded, this, [this, job, data, packCode] {
             ModpackList packs;
             parseAndAddPacks(*data, PackType::Private, packs);
-            foreach (Modpack currentPack, packs) {
+            for (auto& currentPack : packs) {
                 currentPack.packCode = packCode;
                 emit privateFileDownloadFinished(currentPack);
             }

launcher/modplatform/legacy_ftb/PackInstallTask.cpp

@@ -160,7 +160,7 @@ void PackInstallTask::install()
         // we only care about the libs
         QJsonArray libs = doc.object().value("libraries").toArray();
 
-        foreach (const QJsonValue& value, libs) {
+        for (const auto& value : libs) {
             QString nameValue = value.toObject().value("name").toString();
             if (!nameValue.startsWith("net.minecraftforge")) {
                 continue;