MAINT: Fix LGTM.com warning

Comparison result is always the same
Comparison is always false because res <= 0.

Indeed the for(;;) iteration may stop on 3 different breaks:

            res = -1;
            break;

            if (!res) {
                break;

            if (!res) {
                break;

Therefore, after the loop, the only possible values for res are -1 and 0,
and (res > 0) is always false.

This originates in 37dc69c (numpy#17029).

numpy/core/src/multiarray/ctors.c

@@ -2717,7 +2717,7 @@ PyArray_CopyAsFlat(PyArrayObject *dst, PyArrayObject *src, NPY_ORDER order)
         /* If we exhausted the dst block, refresh it */
         if (dst_count == count) {
             res = dst_iternext(dst_iter);
-            if (!res) {
+            if (res == 0) {
                 break;
             }
             dst_count = *dst_countptr;
@@ -2731,7 +2731,7 @@ PyArray_CopyAsFlat(PyArrayObject *dst, PyArrayObject *src, NPY_ORDER order)
         /* If we exhausted the src block, refresh it */
         if (src_count == count) {
             res = src_iternext(src_iter);
-            if (!res) {
+            if (res == 0) {
                 break;
             }
             src_count = *src_countptr;
@@ -2748,10 +2748,6 @@ PyArray_CopyAsFlat(PyArrayObject *dst, PyArrayObject *src, NPY_ORDER order)
     NPY_cast_info_xfree(&cast_info);
     NpyIter_Deallocate(dst_iter);
     NpyIter_Deallocate(src_iter);
-    if (res > 0) {
-        /* The iteration stopped successfully, do not report an error */
-        return 0;
-    }
     return res;
 }