doc: updated fs

nodejs#5862
removed irrelevant data about fs.readFile

doc/api/fs.markdown

@@ -620,7 +620,7 @@ Synchronous readdir(3). Returns an array of filenames excluding `'.'` and
 
 ## fs.readFile(file[, options], callback)
 
-* `file` {String | Integer} filename or file descriptor
+* `file` {String} filename
 * `options` {Object | String}
   * `encoding` {String | Null} default = `null`
   * `flag` {String} default = `'r'`
@@ -646,10 +646,6 @@ If `options` is a string, then it specifies the encoding. Example:
 fs.readFile('/etc/passwd', 'utf8', callback);
 ```
 
-Any specified file descriptor has to support reading.
-
-_Note: Specified file descriptors will not be closed automatically._
-
 ## fs.readFileSync(file[, options])
 
 Synchronous version of [`fs.readFile`][]. Returns the contents of the `file`.