stream: fix the spellings

Author: antsmartian

lib/_stream_duplex.js

@@ -20,8 +20,8 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // a duplex stream is just a stream that is both readable and writable.
-// Since JS doesn't have multiple prototypal inheritance, this class
-// prototypally inherits from Readable, and then parasitically from
+// Since JS doesn't have multiple prototype inheritance, this class
+// prototypically inherits from Readable, and then parasitically from
 // Writable.
 
 'use strict';