[dovecot/core] 01f121: lib: test-utc-mktime: Remove duplicate test

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: 01f121754efa88302cf6dfbfd49f7c0efde0e944
      https://github.com/dovecot/core/commit/01f121754efa88302cf6dfbfd49f7c0efde0e944
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-06-06 (Tue, 06 Jun 2017)

  Changed paths:
    M src/lib/test-utc-mktime.c

  Log Message:
  -----------
  lib: test-utc-mktime: Remove duplicate test

Also fixes a compiler warning when time_t is signed 32bit.