Update dependencies for 4.0.x line

Author: Garion Herman

composer.json

@@ -30,17 +30,14 @@
         "silverstripe/admin": "^1.1",
         "silverstripe/siteconfig": "^4.1",
         "defuse/php-encryption": "^2.2",
-        "silverstripe/login-forms": "1.x-dev",
-        "silverstripe/security-extensions": "1.x-dev"
+        "silverstripe/login-forms": "^4.0",
+        "silverstripe/security-extensions": "^4.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^5.7",
         "squizlabs/php_codesniffer": "^3.0"
     },
     "extra": {
-        "branch-alias": {
-            "dev-master": "4.0.x-dev"
-        },
         "expose": [
             "client/dist"
         ]