Blob#slice doc fix

Author: faveoled

dom/src/main/scala/org/scalajs/dom/Blob.scala

@@ -35,7 +35,7 @@ class Blob(blobParts: js.Iterable[BlobPart], options: BlobPropertyBag = js.nativ
     */
   def `type`: String = js.native
 
-  /** A string indicating the MIME type of the data contained in the Blob. If the type is unknown, this string is empty.
+  /** Creates and returns a new Blob object which contains data from a subset of the blob on which it's called.
     */
   def slice(start: Double = js.native, end: Double = js.native, contentType: String = js.native): Blob = js.native