Fix return type of revokeTokens

This was a mistake in 97186e7; the API response is a single BatchResult. The
single-specifier variant is now redundant so I’ve removed that too.

textile/features.textile

@@ -259,7 +259,7 @@ h3(#rest-auth). Auth
 * @(RSA17)@ @Auth#revokeTokens@ function:
 ** @(RSA17a)@ Takes a @TokenRevocationTargetSpecifier@ or an array of @TokenRevocationTargetSpecifier@s and sends them in a POST request to /keys/{API_KEY_NAME}/revokeTokens, with the newBatchResponse query param set to "true", where @API_KEY_NAME@ is the API key name obtained by reading @AuthOptions#key@ up until the first @:@ character.
 ** @(RSA17b)@ The @TokenRevocationTargetSpecifier@s should be mapped to strings by joining the @type@ and @value@ with a ":" character and sent in the @targets@ field of the request body
-** @(RSA17c)@ Returns an array of @BatchResult<TokenRevocationSuccessResult | TokenRevocationFailureResult>@s. Optionally, in languages where this is idiomatic, an overload may be implemented whereby the method can be called with a single @TokenRevocationTargetSpecifier@ and return a single @BatchResult<TokenRevocationSuccessResult | TokenRevocationFailureResult>@. This is not a feature of the REST API, whose response will still be an array, so if implementing this overload, the SDK will have to extract the element from the array.
+** @(RSA17c)@ Returns a @BatchResult<TokenRevocationSuccessResult | TokenRevocationFailureResult>@s.
 ** @(RSA17d)@ If called from a client using token authentication, should raise an @ErrorInfo@ with a @40162@ error code and @401@ status code
 ** @(RSA17e)@ Accepts an optional @issuedBefore@ timestamp, represented as milliseconds since the epoch, or a `Time` object if idiomatic to the language
 ** @(RSA17f)@ If an @allowReauthMargin@ boolean is supplied, it should be included in the @allowReauthMargin@ field of the request body
@@ -1901,8 +1901,7 @@ class Auth: // RSA*
   createTokenRequest(TokenParams?, AuthOptions?) => io TokenRequest // RSA9
   requestToken(TokenParams?, AuthOptions?) => io TokenDetails // RSA8
   tokenDetails: TokenDetails? // RSA16
-  revokeTokens(TokenRevocationTargetSpecifier, issuedBefore Time?, allowReauthMargin boolean?) => io BatchResult<TokenRevocationSuccessResult | TokenRevocationFailureResult> // RSA17
-  revokeTokens(TokenRevocationTargetSpecifier[], issuedBefore Time?, allowReauthMargin boolean?) => io BatchResult<TokenRevocationSuccessResult | TokenRevocationFailureResult>[] // RSA17
+  revokeTokens(TokenRevocationTargetSpecifier[], issuedBefore Time?, allowReauthMargin boolean?) => io BatchResult<TokenRevocationSuccessResult | TokenRevocationFailureResult> // RSA17
 
 class TokenDetails: // TD*
   +fromJson(String | JsonObject) -> TokenDetails // TD7