doc: remove redundant parameter comments from fs

Some old version parameter comments are left in fs.markdown. Remove
them.

PR-URL: #5952
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Robert Lindstädt <robert.lindstaedt@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

doc/api/fs.markdown

@@ -821,9 +821,6 @@ The callback is given the three arguments, `(err, bytesRead, buffer)`.
   * `encoding` {String} default = `'utf8'`
 * `callback` {Function}
 
-* `path` {String}
-* `callback` {Function}
-
 Asynchronous readdir(3).  Reads the contents of a directory.
 The callback gets two arguments `(err, files)` where `files` is an array of
 the names of the files in the directory excluding `'.'` and `'..'`.
@@ -839,8 +836,6 @@ the filenames returned will be passed as `Buffer` objects.
 * `options` {String | Object}
   * `encoding` {String} default = `'utf8'`
 
-* `path` {String}
-
 Synchronous readdir(3). Returns an array of filenames excluding `'.'` and
 `'..'`.
 
@@ -900,9 +895,6 @@ string. Otherwise it returns a buffer.
   * `encoding` {String} default = `'utf8'`
 * `callback` {Function}
 
-* `path` {String}
-* `callback` {Function}
-
 Asynchronous readlink(2). The callback gets two arguments `(err,
 linkString)`.
 
@@ -917,8 +909,6 @@ the link path returned will be passed as a `Buffer` object.
 * `options` {String | Object}
   * `encoding` {String} default = `'utf8'`
 
-* `path` {String}
-
 Synchronous readlink(2). Returns the symbolic link's string value.
 
 The optional `options` argument can be a string specifying an encoding, or an