Docs: Updated standard token filter docs to indicate true behavior: doing nothing

Closes #9300

docs/reference/analysis/tokenfilters/standard-tokenfilter.asciidoc

@@ -5,3 +5,11 @@ A token filter of type `standard` that normalizes tokens extracted with
 the
 <<analysis-standard-tokenizer,Standard
 Tokenizer>>.
+
+[TIP]
+==================================================
+
+The `standard` token filter currently does nothing.  It remains as a placeholder
+in case some filtering function needs to be added in a future version.
+
+==================================================