fetch: removal of redundant condition (nodejs#1821)

Author: debadree25

lib/fetch/body.js

@@ -171,11 +171,6 @@ function extractBody (object, keepalive = false) {
     if (object.type) {
       type = object.type
     }
-  } else if (object instanceof Uint8Array) {
-    // byte sequence
-
-    // Set source to object.
-    source = object
   } else if (typeof object[Symbol.asyncIterator] === 'function') {
     // If keepalive is true, then throw a TypeError.
     if (keepalive) {