add setup with cluster_features

Author: parkertimmins

x-pack/plugin/logsdb/src/yamlRestTest/resources/rest-api-spec/test/patternedtext/20_synthetic_source.yml

@@ -1,8 +1,10 @@
-simple:
+setup:
   - requires:
       cluster_features: [ "mapper.patterned_text" ]
       reason: "patterned_text mappings are used in this test"
 
+---
+simple:
   - do:
       indices.create:
         index: test