Fix incorrect usage of emitFirrtl in test (#1817) (#1818)

Change a test to use emitChirrtl instead of emitFirrtl. This test
isn't supposed to be running the Scala FIRRTL Compiler, but the latter
method causes this to happen.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>
(cherry picked from commit 492a71d6

)

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>