Revert "Include default index option type to defaults"

This reverts commit b08e2a1.

Author: kderusso

server/src/main/java/org/elasticsearch/common/settings/IndexScopedSettings.java

@@ -203,7 +203,6 @@ public final class IndexScopedSettings extends AbstractScopedSettings {
                 IndexSettings.INDEX_MAPPER_SOURCE_MODE_SETTING,
                 IndexSettings.RECOVERY_USE_SYNTHETIC_SOURCE_SETTING,
                 InferenceMetadataFieldsMapper.USE_LEGACY_SEMANTIC_TEXT_FORMAT,
-                InferenceMetadataFieldsMapper.DEFAULT_SEMANTIC_TEXT_INDEX_OPTIONS,
 
                 // validate that built-in similarities don't get redefined
                 Setting.groupSetting("index.similarity.", (s) -> {

server/src/main/java/org/elasticsearch/index/mapper/InferenceMetadataFieldsMapper.java

@@ -22,8 +22,6 @@
 import java.util.Map;
 import java.util.function.Function;
 
-import static org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper.VectorIndexType.BBQ_HNSW;
-
 /**
  * An abstract {@link MetadataFieldMapper} used as a placeholder for implementation
  * in the inference module. It is required by {@link SourceFieldMapper} to identify
@@ -44,14 +42,6 @@ public abstract class InferenceMetadataFieldsMapper extends MetadataFieldMapper
         Setting.Property.InternalIndex
     );
 
-    public static final Setting<String> DEFAULT_SEMANTIC_TEXT_INDEX_OPTIONS = Setting.simpleString(
-        "index.mapping.semantic_text.default_index_options_type",
-        BBQ_HNSW.getName(),
-        Setting.Property.Final,
-        Setting.Property.IndexScope,
-        Setting.Property.InternalIndex
-    );
-
     // Check index version SOURCE_MAPPER_MODE_ATTRIBUTE_NOOP because that index version was added in the same serverless promotion
     // where the new format was enabled by default
     public static final IndexVersion USE_NEW_SEMANTIC_TEXT_FORMAT_BY_DEFAULT = IndexVersions.SOURCE_MAPPER_MODE_ATTRIBUTE_NOOP;