MDL-71622 behat: use own fork of friends-of-behat/mink-extension

Upstream behat/mink-extension isn't updated since 2018.

So we switch to friends-of-behat/mink-extension until
upstream situation is clarified.

But friends-of-behat/mink-extension has some PHP8 issues
that, at the time of writting this, have not been solved:

- https://github.com/FriendsOfBehat/MinkExtension/pull/9

So we are temporarily changing to one fork:

https://github.com/moodlehq/MinkExtension

Whenever those issues are solved by friends-of-beha or behat
we will change back to them and remove our fork.

Generated with composer 2.x and PHP 7.3

composer.json

@@ -4,9 +4,15 @@
     "description": "Moodle - the world's open source learning platform",
     "type": "project",
     "homepage": "https://moodle.org",
+    "repositories": [
+        {
+            "type": "vcs",
+            "url": "https://github.com/moodlehq/MinkExtension.git"
+        }
+    ],
     "require-dev": {
         "phpunit/phpunit": "9.5.*",
-        "moodlehq/behat-extension": "3.311.4",
+        "moodlehq/behat-extension": "3.311.5",
         "mikey179/vfsstream": "^1.6"
     },
     "minimum-stability": "dev",