remove unnecessary index creation in yaml tests

Author: Samiul-TheSoccerFan

x-pack/plugin/inference/src/yamlRestTest/resources/rest-api-spec/test/inference/30_semantic_text_inference_bwc.yml

@@ -657,32 +657,17 @@ setup:
       cluster_features: semantic_text.skip_inference_fields
       reason: Skip _inference_fields when search is performed on legacy semantic_text format.
 
-  - do:
-      indices.create:
-        index: test-skip-inference_field-index
-        body:
-          settings:
-            index:
-              mapping:
-                semantic_text:
-                  use_legacy_format: true
-          mappings:
-            properties:
-              inference_field:
-                type: semantic_text
-                inference_id: sparse-inference-id
-
   - do:
       index:
-        index: test-skip-inference_field-index
+        index: test-index
         id: doc_1
         body:
-          inference_field: "test value"
+          sparse_field: "test value"
         refresh: true
 
   - do:
       search:
-        index: test-skip-inference_field-index
+        index: test-index
         body:
           fields: [ _inference_fields ]
           query: