Fix PhoneticTokenFilter (#2589)

Author: flobernd

specification/_types/analysis/phonetic-plugin.ts

@@ -64,7 +64,7 @@ export enum PhoneticRuleType {
 export class PhoneticTokenFilter extends TokenFilterBase {
   type: 'phonetic'
   encoder: PhoneticEncoder
-  languageset: PhoneticLanguage[]
+  languageset: PhoneticLanguage | PhoneticLanguage[]
   max_code_len?: integer
   name_type: PhoneticNameType
   replace?: boolean