Update comment

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -788,7 +788,7 @@ class ClassfileParser(
       if (scan(tpnme.TASTYATTR)) {
         val attrLen = in.nextInt
         val bytes = in.nextBytes(attrLen)
-        if (bytes.length == 16) { // A tasty attribute with that has only a UUID implies the existence of the .tasty file
+        if (attrLen == 16) { // A tasty attribute with that has only a UUID (16 bytes) implies the existence of the .tasty file
           val tastyBytes: Array[Byte] = classfile.underlyingSource match { // TODO: simplify when #3552 is fixed
             case None =>
               ctx.error("Could not load TASTY from .tasty for virtual file " + classfile)