t-reftable-pq: make merged_iter_pqueue_check() static

merged_iter_pqueue_check() is a function previously defined in
reftable/pq_test.c (now t/unit-tests/t-reftable-pq.c) and used in
the testing of a priority queue as defined by reftable/pq.{c, h}.
As such, this function is only called by reftable/pq_test.c and it
makes little sense to expose it to non-testing code via reftable/pq.h.

Hence, make this function static and remove its prototype from
reftable/pq.h.

Mentored-by: Patrick Steinhardt <[email protected]>
Mentored-by: Christian Couder <[email protected]>
Signed-off-by: Chandra Pratap <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Chandra Pratap

reftable/pq.h

@@ -22,7 +22,6 @@ struct merged_iter_pqueue {
 	size_t cap;
 };
 
-void merged_iter_pqueue_check(struct merged_iter_pqueue pq);
 struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq);
 void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry *e);
 void merged_iter_pqueue_release(struct merged_iter_pqueue *pq);

t/unit-tests/t-reftable-pq.c

@@ -10,7 +10,7 @@ license that can be found in the LICENSE file or at
 #include "reftable/constants.h"
 #include "reftable/pq.h"
 
-void merged_iter_pqueue_check(struct merged_iter_pqueue pq)
+static void merged_iter_pqueue_check(struct merged_iter_pqueue pq)
 {
 	for (size_t i = 1; i < pq.len; i++) {
 		size_t parent = (i - 1) / 2;