reftable: remove unnecessary curly braces in reftable/pq.c

reftable: remove unnecessary curly braces in reftable/pq.c

According to Documentation/CodingGuidelines, control-flow statements
with a single line as their body must omit curly braces. Make
reftable/pq.c conform to this guideline. Besides that, remove
unnecessary newlines and variable assignment.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>