Fix Markdown syntax in ClusterHealthRequest (#2768)

Author: pquentin

specification/cluster/health/ClusterHealthRequest.ts

@@ -41,7 +41,7 @@ import { Duration } from '@_types/Time'
 export interface Request extends RequestBase {
   path_parts: {
     /**
-     * Comma-separated list of data streams, indices, and index aliases used to limit the request. Wildcard expressions (*) are supported. To target all data streams and indices in a cluster, omit this parameter or use _all or *.
+     * Comma-separated list of data streams, indices, and index aliases used to limit the request. Wildcard expressions (`*`) are supported. To target all data streams and indices in a cluster, omit this parameter or use _all or `*`.
      */
     index?: Indices
   }