validation: don't erase coins cache on prune flushes

src/validation.cpp

@@ -2902,7 +2902,7 @@ bool Chainstate::FlushStateToDisk(
                 return FatalError(m_chainman.GetNotifications(), state, _("Disk space is too low!"));
             }
             // Flush the chainstate (which may refer to block index entries).
-            const auto empty_cache{(mode == FlushStateMode::ALWAYS) || fCacheLarge || fCacheCritical || fFlushForPrune};
+            const auto empty_cache{(mode == FlushStateMode::ALWAYS) || fCacheLarge || fCacheCritical};
             if (empty_cache ? !CoinsTip().Flush() : !CoinsTip().Sync()) {
                 return FatalError(m_chainman.GetNotifications(), state, _("Failed to write to coin database."));
             }