(maint) cleanup fixtures format

Author: h0tw1r3

.fixtures.yml

@@ -1,7 +1,8 @@
+---
 fixtures:
   repositories:
-    "stdlib": "https://github.com/puppetlabs/puppetlabs-stdlib"
-    "cron_core": "https://github.com/puppetlabs/puppetlabs-cron_core.git"
-    "facts": "https://github.com/puppetlabs/puppetlabs-facts.git"
-    "provision": "https://github.com/puppetlabs/provision.git"
-    puppet_agent: 'https://github.com/puppetlabs/puppetlabs-puppet_agent.git'
+    stdlib: https://github.com/puppetlabs/puppetlabs-stdlib
+    cron_core: https://github.com/puppetlabs/puppetlabs-cron_core.git
+    facts: https://github.com/puppetlabs/puppetlabs-facts.git
+    provision: https://github.com/puppetlabs/provision.git
+    puppet_agent: https://github.com/puppetlabs/puppetlabs-puppet_agent.git