update WP Codex and license links [skip ci]

LICENSE.md

@@ -357,5 +357,5 @@ into proprietary programs. If your program is a subroutine library,
 you may consider it more useful to permit linking proprietary
 applications with the library. If this is what you want to do, use the
 [GNU Lesser General Public
-License](http://www.gnu.org/licenses/lgpl.html) instead of this
+License](https://www.gnu.org/licenses/lgpl.html) instead of this
 License.

README.md

@@ -10,7 +10,7 @@
 * Requires PHP:      5.5
 * Stable tag:        1.4.4
 * License:           GPLv2 or later
-* License URI:       http://www.gnu.org/licenses/gpl-2.0.html
+* License URI:       https://www.gnu.org/licenses/gpl-2.0.html
 
 ## Description ##
 A blacklist extension for the famous [Statify](https://wordpress.org/plugins/statify/) Wordpress plugin.
@@ -45,7 +45,7 @@ The plugin is capable of handling multisite installations.
 * Special Thanks to [pluginkollektiv](https://github.com/pluginkollektiv) for maintaining _Statify_
 
 ## Installation ##
-* If you don’t know how to install a plugin for WordPress, [here’s how](http://codex.wordpress.org/Managing_Plugins#Installing_Plugins).
+* If you don’t know how to install a plugin for WordPress, [here’s how](https://wordpress.org/support/article/managing-plugins/#installing-plugins).
 * Make sure _Statify_ plugin is installed and active 
 * Goto _Settings_ -> _Statify Blacklist_ to configure the plugin
 

statify-blacklist.php

@@ -27,7 +27,7 @@
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
- * along with Statify Blacklist. If not, see http://www.gnu.org/licenses/gpl-2.0.html.
+ * along with Statify Blacklist. If not, see https://www.gnu.org/licenses/gpl-2.0.html.
  */
 
 // Quit if accessed directly.