Named argument `dialect` does not exist in signature SEARCH

Specifying dialect argument in SEARCH function with spanner emulator crash.

For instance:

`SEARCH(S.textFulltextTokens, @query, dialect=>"words_phrase")`

Gives

```
Caused by: io.grpc.StatusRuntimeException: INVALID_ARGUMENT: No matching signature for function SPANNER:SEARCH

Argument types: TOKENLIST, STRING, dialect => STRING
Signature: SEARCH([tokens=>]TOKENLIST, [query=>]STRING, [enhance_query => BOOL], [language_tag => STRING])
Named argument `dialect` does not exist in signature [at 10:7]
AND SEARCH(S.textFulltextTokens, @query, dialect=>"words_phrase")
^
```

Looking at the Signature from the error, dialect argument is not listed.