[Tests] Remove skip tests in search/30_limits.yml

After backporting the related change to the 6.x branches, this test can now also
be run in a mixed cluster.

Relates to #26574

rest-api-spec/src/main/resources/rest-api-spec/test/search/30_limits.yml

@@ -1,4 +1,11 @@
 setup:
+  - do:
+      indices.create:
+          index: test_1
+          body:
+            settings:
+              index.max_docvalue_fields_search: 2
+
   - do:
       index:
           index:  test_1
@@ -53,21 +60,11 @@ setup:
 
 ---
 "Docvalues_fields size limit":
-  - skip:
-      version: " - 6.99.99"
-      reason: soft limit for docvalue_fields only available as of 7.0.0
-
-  - do:
-      indices.create:
-          index: test_2
-          body:
-            settings:
-              index.max_docvalue_fields_search: 2
 
   - do:
       catch:      /Trying to retrieve too many docvalue_fields\. Must be less than or equal to[:] \[2\] but was \[3\]\. This limit can be set by changing the \[index.max_docvalue_fields_search\] index level setting\./
       search:
-        index: test_2
+        index: test_1
         body:
           query:
             match_all: {}