Bump phpunit/phpunit from 6.5.5 to 6.5.6

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 6.5.5 to 6.5.6.
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/master/ChangeLog-5.7.md)
- [Commits](https://github.com/sebastianbergmann/phpunit/compare/6.5.5...6.5.6)

composer.lock

@@ -49,12 +49,12 @@
             "source": {
                 "type": "git",
                 "url": "https://github.com/ChristophWurst/nextcloud_composer.git",
-                "reference": "d1e6ed5af656b309ee7c355209318304cba0f133"
+                "reference": "b553b6cf4002f2ba605d259dae4638525f7bc507"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/ChristophWurst/nextcloud_composer/zipball/d1e6ed5af656b309ee7c355209318304cba0f133",
-                "reference": "d1e6ed5af656b309ee7c355209318304cba0f133",
+                "url": "https://api.github.com/repos/ChristophWurst/nextcloud_composer/zipball/b553b6cf4002f2ba605d259dae4638525f7bc507",
+                "reference": "b553b6cf4002f2ba605d259dae4638525f7bc507",
                 "shasum": ""
             },
             "type": "library",
@@ -74,7 +74,7 @@
                 }
             ],
             "description": "Composer package containing Nextcloud's public API (classes, interfaces)",
-            "time": "2018-01-18T13:04:59+00:00"
+            "time": "2018-02-01T07:21:07+00:00"
         },
         {
             "name": "doctrine/instantiator",
@@ -743,16 +743,16 @@
         },
         {
             "name": "phpunit/phpunit",
-            "version": "6.5.5",
+            "version": "6.5.6",
             "source": {
                 "type": "git",
                 "url": "https://github.com/sebastianbergmann/phpunit.git",
-                "reference": "83d27937a310f2984fd575686138597147bdc7df"
+                "reference": "3330ef26ade05359d006041316ed0fa9e8e3cefe"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/83d27937a310f2984fd575686138597147bdc7df",
-                "reference": "83d27937a310f2984fd575686138597147bdc7df",
+                "url": "https://api.github.com/repos/sebastianbergmann/phpunit/zipball/3330ef26ade05359d006041316ed0fa9e8e3cefe",
+                "reference": "3330ef26ade05359d006041316ed0fa9e8e3cefe",
                 "shasum": ""
             },
             "require": {
@@ -823,7 +823,7 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2017-12-17T06:31:19+00:00"
+            "time": "2018-02-01T05:57:37+00:00"
         },
         {
             "name": "phpunit/phpunit-mock-objects",