Downgraded to behat/gherkin 4.12

In the subsequent version, files were moved to PSR-4 compliant paths. See Behat/Gherkin#288

Author: SidRoberts

composer.json

@@ -35,7 +35,9 @@
         "codeception/codeception": "~4.0",
         "codeception/module-asserts": "~2.0",
 
-        "squizlabs/php_codesniffer": "~3.4"
+        "squizlabs/php_codesniffer": "~3.4",
+
+        "behat/gherkin": "4.12.0"
     },