Docs: Revise comments using “we” in WordPress root directory files.

This updates some inline comments to better match the guidelines and recommendations set forth in the make/core and make/docs handbooks:

> In general, use second person in your documentation. Second person depicts a friendly tone, with a perfect focus on the reader. In addition to this, directly addressing the reader helps avoid passive voice; thereby preventing unwanted confusion.
> ...
> the word “we” should be avoided (...) unless its made very clear which group is speaking.

Includes:
* Replacing first-person usage of "we" with second person point of view.
* Making small clarification adjustments where the voice is much too casual or lacks clear context, especially for non-native English speakers.

References:
* [https://make.wordpress.org/docs/style-guide/language-grammar/grammatical-person/ Style Guide: Grammatical person]
* [https://make.wordpress.org/docs/handbook/documentation-team-handbook/handbooks-style-and-formatting-guide/ Handbooks & HelpHub Style and Formatting Guide]
* [https://make.wordpress.org/core/handbook/best-practices/post-comment-guidelines/#style-and-substance Post & Comment Guidelines: Style and Substance]

Follow-up to [2176], [3430], [4676], [6009], [7991], [12688], [12762], [26008], [28978], [44488], [44962], [51979], [53131], [53132], [53156], [53131], [54200].

Props ironprogrammer, costdev, jorbin, SergeyBiryukov.
See #57052.

git-svn-id: https://develop.svn.wordpress.org/trunk@54866 602fd350-edb4-49c9-b593-d223f7449a82

src/xmlrpc.php

@@ -12,7 +12,7 @@
  */
 define( 'XMLRPC_REQUEST', true );
 
-// Some browser-embedded clients send cookies. We don't want them.
+// Discard unneeded cookies sent by some browser-embedded clients.
 $_COOKIE = array();
 
 // $HTTP_RAW_POST_DATA was deprecated in PHP 5.6 and removed in PHP 7.0.