Revert "eth: drop eth/65, the last non-reqid protocol version" (#23426)

eth/sync_test.go

@@ -28,6 +28,7 @@ import (
 )
 
 // Tests that fast sync is disabled after a successful sync cycle.
+func TestFastSyncDisabling65(t *testing.T) { testFastSyncDisabling(t, eth.ETH65) }
 func TestFastSyncDisabling66(t *testing.T) { testFastSyncDisabling(t, eth.ETH66) }
 
 // Tests that fast sync gets disabled as soon as a real block is successfully