Drop question mark suffix from optional PHPDoc @param types

Summary:
The question mark in `@param type? $foo Desc` is a custom notation not consistently applied across the codebase and not necessarily obvious to the reader (because custom and not mentioned in https://github.com/php-fig/fig-standards/blob/master/proposed/phpdoc.md ).
Instead, explicitly state "optional" in the parameter description for clarity.

Closes T15925.

Test Plan: Run PHPStan, see no `PHPDoc @param has invalid value (type? [...]` style output anymore.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15925

Differential Revision: https://we.phorge.it/D25798

src/channel/PhutilSocketChannel.php

@@ -35,7 +35,7 @@ final class PhutilSocketChannel extends PhutilChannel {
    *
    * @param socket  Socket (stream socket, not plain socket). If only one
    *                socket is provided, it is used for reading and writing.
-   * @param socket? Optional write socket.
+   * @param socket  (optional) Write socket.
    *
    * @task construct
    */

src/filesystem/TempFile.php

@@ -27,11 +27,13 @@ final class TempFile extends Phobject {
   /**
    * Create a new temporary file.
    *
-   * @param string? Filename hint. This is useful if you intend to edit the
-   *                file with an interactive editor, so the user's editor shows
-   *                "commit-message" instead of "p3810hf-1z9b89bas".
-   * @param string? Root directory to hold the file. If omitted, the system
-   *                temporary directory (often "/tmp") will be used by default.
+   * @param string  (optional) Filename hint. This is useful if you intend to
+   *                edit the file with an interactive editor, so the user's
+   *                editor shows "commit-message" instead of
+   *                "p3810hf-1z9b89bas".
+   * @param string  (optional) Root directory to hold the file. If omitted, the
+   *                system temporary directory (often "/tmp") will be used by
+   *                default.
    * @task create
    */
   public function __construct($filename = null, $root_directory = null) {