Require PHP 7.0 for tests installing WP via Composer (wp-cli#5825)

* Require PHP 7.0 for tests installing WP via Composer

They install the latest WP version, which now requires PHP 7.0

* Fix typo

features/bootstrap.feature

@@ -317,6 +317,7 @@ Feature: Bootstrap WP-CLI
       1
       """
 
+  @require-php-7.0
   Scenario: Composer stack with both WordPress and wp-cli as dependencies (command line)
     Given a WP installation with Composer
     And a dependency on current wp-cli
@@ -329,13 +330,14 @@ Feature: Bootstrap WP-CLI
       WP CLI Site with both WordPress and wp-cli as Composer dependencies
       """
 
-  @broken
+  @broken @require-php-7.0
   Scenario: Composer stack with both WordPress and wp-cli as dependencies (web)
     Given a WP installation with Composer
     And a dependency on current wp-cli
     And a PHP built-in web server to serve 'WordPress'
     Then the HTTP status code should be 200
 
+  @require-php-7.0
   Scenario: Composer stack with both WordPress and wp-cli as dependencies and a custom vendor directory
     Given a WP installation with Composer and a custom vendor directory 'vendor-custom'
     And a dependency on current wp-cli