fix comment to reflect the implementation I ended up settling on.

Thanks to Duncan for noticing this

llvm-svn: 68518

llvm/include/llvm/Bitcode/BitCodes.h

@@ -89,7 +89,7 @@ public:
     VBR   = 2,  // A VBR field where Val specifies the width of each chunk.
     Array = 3,  // A sequence of fields, next field species elt encoding.
     Char6 = 4,  // A 6-bit fixed field which maps to [a-zA-Z0-9._].
-    Blob  = 5   // 8-bit aligned array of 8-bit characters.
+    Blob  = 5   // 32-bit aligned array of 8-bit characters.
   };
 
   explicit BitCodeAbbrevOp(uint64_t V) :  Val(V), IsLiteral(true) {}