Merge pull request #2111 from OffchainLabs/finalize-arbos-20

Finalize ArbOS 20

arbos/arbosState/arbosstate.go

@@ -318,18 +318,10 @@ func (state *ArbosState) UpgradeArbosVersion(
 			}
 		// ArbOS versions 12 through 19 are left to Orbit chains for custom upgrades.
 		case 20:
-			if !chainConfig.DebugMode() {
-				// This upgrade isn't finalized so we only want to support it for testing
-				return fmt.Errorf(
-					"the chain is upgrading to unsupported ArbOS version %v, %w",
-					nextArbosVersion,
-					ErrFatalNodeOutOfDate,
-				)
-			}
 			// Update Brotli compression level for fast compression from 0 to 1
 			ensure(state.SetBrotliCompressionLevel(1))
 		default:
-			if nextArbosVersion >= 12 && state.arbosVersion < 20 {
+			if nextArbosVersion >= 12 && nextArbosVersion <= 19 {
 				// ArbOS versions 12 through 19 are left to Orbit chains for custom upgrades.
 			} else {
 				return fmt.Errorf(