pgsql: Remove superfluous newlines in function prototypes.

Remove superfluous newlines in function prototypes.

These were introduced by pgindent due to fixe to broken
indentation (c.f. 8255c7a5eeba8). Previously the mis-indentation of
function prototypes was creatively used to reduce indentation in a few
places.

As that formatting only exists in master and REL_12_STABLE, it seems
better to fix it in both, rather than having some odd indentation in
v12 that somebody might copy for future patches or such.

Author: Andres Freund
Discussion: https://postgr.es/m/20190728013754.jwcbe5nfyt3533vx@alap3.anarazel.de
Backpatch: 12-

Branch
------
REL_12_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/c4b7bb3cf19f5d847544de93c36329de8e59193b

Modified Files
--------------
src/backend/commands/event_trigger.c | 3 +--
src/backend/executor/nodeBitmapHeapscan.c | 6 ++----
src/backend/libpq/auth.c | 3 +--
src/backend/storage/ipc/sinval.c | 3 +--
src/backend/utils/adt/jsonpath_exec.c | 6 ++----
src/include/access/gist_private.h | 3 +--
src/include/replication/logical.h | 9 +++------
src/include/replication/reorderbuffer.h | 15 +++++----------
src/include/storage/sinval.h | 3 +--
src/include/utils/guc.h | 15 +++++----------
10 files changed, 22 insertions(+), 44 deletions(-)