Reviewers: Suppress FutureReturnValueIgnored warning

When all error prone warnings are enabled the FutureReturnValueIgnored
bug pattern is reported:

  plugins/reviewers/src/main/java/com/googlesource/gerrit/plugins/reviewers/Reviewers.java:161:
  error: [FutureReturnValueIgnored] Return value of methods returning Future must be checked.
  Ignoring returned Futures suppresses exceptions thrown from the code that completes the Future.
      workQueue.getDefaultQueue().submit(task);
                                        ^
    (see https://errorprone.info/bugpattern/FutureReturnValueIgnored)
  Did you mean to remove this line?

Change-Id: Ib4f6f3f437eb5ca9da366ac40a587604fd4e2ad3
1 file changed