Bump to current Behat 3.6.1

Also update other dependencies to actual ones.

Special mention to symfony/process raised to 4.x or 5.x
so it only can run with php71 or newer.

Hence, this only can be backported to Moodle 3.7 and up.

Author: stronk7

composer.json

@@ -15,11 +15,11 @@
     "require": {
         "php": ">=7.2.0",
         "behat/mink": "~1.8",
-        "behat/mink-extension": "~2.2",
+        "behat/mink-extension": "~2.3",
         "behat/mink-goutte-driver": "~1.2",
-        "behat/mink-selenium2-driver": "~1.3",
-        "symfony/process": "2.8.*",
-        "behat/behat": "3.5.*"
+        "behat/mink-selenium2-driver": "~1.4",
+        "symfony/process": "^4.0 || ^5.0",
+        "behat/behat": "3.6.*"
     },
     "autoload": {
         "psr-0": {