bpo-31849: Fix warning in pyhash.c (GH-6799)

(cherry picked from commit a8eb58546b37a7cd5f332f019bb07388f5212c2d)

Co-authored-by: A. Jesse Jiryu Davis <jesse@emptysquare.net>
diff --git a/Python/pyhash.c b/Python/pyhash.c
index 6fc12fd..4c0b929 100644
--- a/Python/pyhash.c
+++ b/Python/pyhash.c
@@ -272,8 +272,8 @@
         x = (_PyHASH_MULTIPLIER * x) ^ (Py_uhash_t) *p++;
     x ^= (Py_uhash_t) len;
     x ^= (Py_uhash_t) _Py_HashSecret.fnv.suffix;
-    if (x == -1) {
-        x = -2;
+    if (x == (Py_uhash_t) -1) {
+        x = (Py_uhash_t) -2;
     }
     return x;
 }