Update binary.md forgotten when adding language version fields to binary

Change-Id: I243881923c55229f1e03901f2f655cba99633e3c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112086
Reviewed-by: Dmitry Stefantsov <[email protected]>
Commit-Queue: Jens Johansen <[email protected]>

Author: jensjoha

pkg/kernel/binary.md

@@ -224,6 +224,8 @@ type Name {
 
 type Library {
   Byte flags (isExternal, isSynthetic);
+  UInt languageVersionMajor;
+  UInt languageVersionMinor;
   CanonicalNameReference canonicalName;
   StringReference name;
   // An absolute path URI to the .dart file from which the library was created.