Update src/connections.jl

Co-authored-by: Eric Davies <iamed2@gmail.com>

Author: pankgeorg

src/connections.jl

@@ -817,7 +817,7 @@ Do the flush dance described in the libpq docs. Required when the
 connections are set to nonblocking and we want do send queries/data
 without blocking.
 
-https://www.postgresql.org/docs/current/libpq-async.html#LIBPQ-PQFlush
+https://www.postgresql.org/docs/current/libpq-async.html#LIBPQ-PQFLUSH
 """
 function flush(jl_conn)
     watcher = FDWatcher(socket(jl_conn), true, true)  # can wait for reads and writes