Add a note to the docs that _cat api `help` option cannot be used if an optional url param is used (#28686)

docs/reference/cat.asciidoc

@@ -55,7 +55,7 @@ GET /_cat/master?help
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 // CONSOLE
 
-Might respond respond with:
+Might respond with:
 
 [source,txt]
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@@ -66,6 +66,11 @@ node | n | node name
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 // TESTRESPONSE[s/[|]/[|]/ _cat]
 
+NOTE: `help` is not supported if any optional url parameter is used.
+For example `GET _cat/shards/twitter?help` or `GET _cat/indices/twi*?help`
+results in an error. Use `GET _cat/shards?help` or `GET _cat/indices?help`
+instead.
+
 [float]
 [[headers]]
 === Headers