message: fix(common): remove useless guard in HttpClient
  An invalid "if" condition is always true, and is thus useless. This
  change removes it. No behavior changes.
  Fixes
  PR Close
diff: @@ -352,13 +352,11 @@ export class HttpClient {
  // Figure out the headers.
  let headers: HttpHeaders|undefined = undefined;
  - if (!!options.headers !== undefined) {
  if (options.headers instanceof HttpHeaders) {
  headers = options.headers;
  } else {
  headers = new HttpHeaders(options.headers);
  }
  - }
  // Sort out parameters.
  let params: HttpParams|undefined = undefined;
  