Merge bitcoin-core/secp256k1#1657: tests: remove unused uncounting_illegal_callback_fn

51907fa918 tests: remove unused uncounting_illegal_callback_fn (Jonas Nick)

Pull request description:

ACKs for top commit:
  real-or-random:
    utACK https://github.com/bitcoin-core/secp256k1/pull/1657/commits/51907fa91875b8fd34cb23ec6c23793f7ea92949

Tree-SHA512: 6959671e31938be833eb17ee762aa6d0e7b6789c951058cd32e46bfd95ad96a65625a0b976541b4e6c7d648fdad8af66b8e5503b38fed6387216d281a1513eed

src/tests.c

@@ -87,15 +87,6 @@ static void counting_callback_fn(const char* str, void* data) {
     (*p)++;
 }
 
-static void uncounting_illegal_callback_fn(const char* str, void* data) {
-    /* Dummy callback function that just counts (backwards). */
-    int32_t *p;
-    (void)str;
-    p = data;
-    CHECK(*p != INT32_MIN);
-    (*p)--;
-}
-
 static void run_xoshiro256pp_tests(void) {
     {
         size_t i;