Add skip versions for rank_eval yaml tests

modules/rank-eval/src/test/resources/rest-api-spec/test/rank_eval/10_basic.yml

@@ -1,5 +1,10 @@
 ---
 "Response format":
+
+  - skip:
+      version: " - 6.99.99"
+      reason: the ranking evaluation feature is only available on 7.0
+
   - do:
      indices.create:
          index: foo
@@ -84,6 +89,10 @@
 ---
 "Mean Reciprocal Rank":
 
+  - skip:
+      version: " - 6.99.99"
+      reason: the ranking evaluation feature is only available on 7.0
+
   - do:
      indices.create:
          index: foo

modules/rank-eval/src/test/resources/rest-api-spec/test/rank_eval/20_dcg.yml

@@ -1,6 +1,10 @@
 ---
 "Response format":
 
+  - skip:
+      version: " - 6.99.99"
+      reason: the ranking evaluation feature is only available on 7.0
+
   - do:
       index:
         index:   foo

modules/rank-eval/src/test/resources/rest-api-spec/test/rank_eval/30_failures.yml

@@ -1,6 +1,10 @@
 ---
 "Response format":
 
+  - skip:
+      version: " - 6.99.99"
+      reason: the ranking evaluation feature is only available on 7.0
+
   - do:
       index:
         index:   foo

qa/smoke-test-rank-eval-with-mustache/src/test/resources/rest-api-spec/test/rank-eval/30_template.yml

@@ -1,5 +1,10 @@
 ---
 "Template request":
+
+  - skip:
+      version: " - 6.99.99"
+      reason: the ranking evaluation feature is only available on 7.0
+
   - do:
      indices.create:
          index: foo