Revert "Disable partition check for now, it triggers too often (issue #6251)"

Re-enable partition check, it should be safe again after #6256.

This reverts commit 3eada74d6f.

src/init.cpp

@@ -1416,13 +1416,13 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
 #endif
 
     StartNode(threadGroup, scheduler);
-#if 0 // Disable partition check for now, it triggers too often (issue #6251)
+
     // Monitor the chain, and alert if we get blocks much quicker or slower than expected
     int64_t nPowTargetSpacing = Params().GetConsensus().nPowTargetSpacing;
     CScheduler::Function f = boost::bind(&PartitionCheck, &IsInitialBlockDownload,
                                          boost::ref(cs_main), boost::cref(pindexBestHeader), nPowTargetSpacing);
     scheduler.scheduleEvery(f, nPowTargetSpacing);
-#endif
+
 #ifdef ENABLE_WALLET
     // Generate coins in the background
     if (pwalletMain)