WPCS 2.0.0: Remove the PHPCSAliases file

After extensive testing based on issues which were previously reported, I've concluded that the `PHPCSAliases.php` file can now be safely removed.

Test setup I've used to confirm this:
* Clean Composer install of PHPCS + WPCS _without the `installed_paths` config directive being set.
    ```json
    {
        "require": {},
        "require-dev": {
            "squizlabs/php_codesniffer": "^3.3",
            "wp-coding-standards/wpcs": "^1.1"
        }
    }
    ```
* Basic PHPCS ruleset:
    ```xml
    <?xml version="1.0"?>
    <ruleset name="AliasFileTest">
        <file>.</file>
        <exclude-pattern>vendor/*</exclude-pattern>
        <arg value="p"/>

        <config name="installed_paths" value="vendor/wp-coding-standards/wpcs"/>
        <rule ref="WordPress"/>
    </ruleset>
    ```
* A PHP test file which would generate issues.

Tests I've run:
* Running `vendor/bin/phpcs` on the above (which would be with WPCS 1.2.1) works fine.
* Changed the `config` directive value to point to my local WPCS dev install:
    `<config name="installed_paths" value="I:/path/to/WordPress-Coding-Standards/WordPress-Coding-Standards"/>`
* Tested again against the `develop` branch, still was working fine.
* Now we get to the interesting part: changed to this branch and ran it again. Still working fine.
* Changed the `<rule ref..>` to `<rule ref="WordPress-Core"/>` and still working fine.
* Changed the `<rule ref..>` to `<rule ref="WordPress.Security"/>`, i.e. not a registered standard, but a subcategory and still working fine.

Based on all this, I'm concluding that the WPCS autoloader in the PHPCSAlias file is no longer needed and can now be safely removed.

Refs:
* 1087
* squizlabs/PHP_CodeSniffer 1591

Author: jrfnl

WordPress-Core/ruleset.xml

@@ -3,8 +3,6 @@
 
 	<description>Non-controversial generally-agreed upon WordPress Coding Standards</description>
 
-	<autoload>./../WordPress/PHPCSAliases.php</autoload>
-
 	<!-- Default tab width for indentation fixes and such. -->
 	<arg name="tab-width" value="4"/>
 

WordPress-Extra/ruleset.xml

@@ -3,8 +3,6 @@
 
 	<description>Best practices beyond core WordPress Coding Standards</description>
 
-	<autoload>./../WordPress/PHPCSAliases.php</autoload>
-
 	<rule ref="WordPress-Core"/>
 
 	<!-- Generic PHP best practices.

WordPress/PHPCSAliases.php

@@ -3,8 +3,6 @@
 
 	<description>WordPress Coding Standards</description>
 
-	<autoload>./PHPCSAliases.php</autoload>
-
 	<rule ref="WordPress-Core"/>
 	<rule ref="WordPress-Docs"/>
 	<rule ref="WordPress-Extra"/>