code: public JWSHeader setCritical(List<String> critical) {
          this.critical = critical;
          this.put(HeaderConstants.CRITICAL, critical);
          return this;
      }
docs: Sets the array listing the header parameter names that define extensions that are used in the
  JWS header that MUST be understood and processed or {@code null} for none.
  
  <p>
  Overriding is only supported for the purpose of calling the super implementation and changing
  the return type, but nothing else.
  </p>