Fix spryker build failure (#714)

* Ignore in the phpstan baseline

```
 ------ -----------------------------------------------------------------------
  Line   Pyz/Client/Catalog/CatalogDependencyProvider.php
 ------ -----------------------------------------------------------------------
  147    Parameter #1 $rawCatalogSearchResultFormatterPlugin of class
         Spryker\Client\CatalogPriceProductConnector\Plugin\CurrencyAwareSugge
         stionByTypeResultFormatter constructor expects
         Spryker\Client\Search\Dependency\Plugin\ResultFormatterPluginInterfac
         e,
         Spryker\Client\SearchElasticsearch\Plugin\ResultFormatter\SuggestionB
         yTypeResultFormatterPlugin given.
 ------ -----------------------------------------------------------------------
```

* Downgrade phpstan to 1.6.9 as it is having issues with class_alias()

src/spryker/application/skeleton/composer-harness.json.twig

@@ -16,6 +16,7 @@
     "dmore/chrome-mink-driver": "^2.6",
     "jakoch/phantomjs-installer": "^3.0",
     "roave/better-reflection": "^4.3.0",
+    "phpstan/phpstan": "~1.6.9",
     "phpcompatibility/php-compatibility": "dev-master",
     "sensiolabs/behat-page-object-extension": "^2.3",
     "guzzlehttp/guzzle": "^6.3.0",