buffer: improve Blob constructor error message when passing a string

resolve: nodejs#38856

PR-URL: nodejs#42338
Fixes: nodejs#38856
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: meixg

lib/internal/blob.js

@@ -138,7 +138,7 @@ class Blob {
     if (sources === null ||
         typeof sources[SymbolIterator] !== 'function' ||
         typeof sources === 'string') {
-      throw new ERR_INVALID_ARG_TYPE('sources', 'Iterable', sources);
+      throw new ERR_INVALID_ARG_TYPE('sources', 'a sequence', sources);
     }
     validateObject(options, 'options');
     let {