[DOCS] Add data streams to validate query API (#59420)

docs/reference/search/validate.asciidoc

@@ -13,7 +13,7 @@ GET twitter/_validate/query?q=user:foo
 [[search-validate-api-request]]
 ==== {api-request-title}
 
-`GET /<index>/_validate/<query>`
+`GET /<target>/_validate/<query>`
 
 
 [[search-validate-api-desc]]
@@ -27,7 +27,13 @@ request body.
 [[search-validate-api-path-params]]
 ==== {api-path-parms-title}
 
-include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=index]
+`<target>`::
+(Optional, string)
+Comma-separated list of data streams, indices, and index aliases to search.
+Wildcard (`*`) expressions are supported.
++
+To search all data streams or indices in a cluster, omit this parameter or use
+`_all` or `*`.
 
 include::{es-repo-dir}/rest-api/common-parms.asciidoc[tag=query]