[model] Mention Constructor.isErroneous in binary.md

It wasn't added by oversite. Similar flags for Field and Procedure are
already included in binary.md.

Change-Id: I3f12f170734489bbc72e03f9d7dcfdeef28daa8a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/427760
Commit-Queue: Chloe Stefantsova <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: chloestefantsova

pkg/kernel/binary.md

@@ -415,7 +415,7 @@ type Constructor extends Member {
   FileOffset startFileOffset; // Offset of the start of the constructor including any annotations.
   FileOffset fileOffset; // Offset of the constructor name.
   FileOffset fileEndOffset;
-  Byte flags (isConst, isExternal, isSynthetic);
+  Byte flags (isConst, isExternal, isSynthetic, isErroneous);
   Name name;
   List<Expression> annotations;
   FunctionNode function;