[obs_pipelines] Clarify use_legacy_search_syntax only applies to logs pipelines (#3910)

Co-authored-by: ci.datadog-api-spec <packages@datadoghq.com>

Author: api-clients-generation-pipeline[bot]

.generator/schemas/v2/openapi.yaml

@@ -44118,6 +44118,7 @@ components:
             Set to `true` to continue using the legacy search syntax while migrating filter queries. After migrating all queries to the new syntax, set to `false`.
             The legacy syntax is deprecated and will eventually be removed.
             Requires Observability Pipelines Worker 2.11 or later.
+            Only applies to `logs` pipelines. This field is ignored for `metrics` pipelines.
             See [Upgrade Your Filter Queries to the New Search Syntax](https://docs.datadoghq.com/observability_pipelines/guide/upgrade_your_filter_queries_to_the_new_search_syntax/) for more information.
           type: boolean
       required:

services/observability_pipelines/src/v2/models/ObservabilityPipelineConfig.ts

@@ -35,6 +35,7 @@ export class ObservabilityPipelineConfig {
    * Set to `true` to continue using the legacy search syntax while migrating filter queries. After migrating all queries to the new syntax, set to `false`.
    * The legacy syntax is deprecated and will eventually be removed.
    * Requires Observability Pipelines Worker 2.11 or later.
+   * Only applies to `logs` pipelines. This field is ignored for `metrics` pipelines.
    * See [Upgrade Your Filter Queries to the New Search Syntax](https://docs.datadoghq.com/observability_pipelines/guide/upgrade_your_filter_queries_to_the_new_search_syntax/) for more information.
    */
   "useLegacySearchSyntax"?: boolean;