Type fix in mldsa (#2308)

Change types `uint32_t t0, t1;` to` int32_t t0, t1;` due to potential
overflow in `if (t0 < 9){a[ctr++] = 4 - t0;}` causing cbmc proofs to
fail.

### Issues:
From pq-code-package/mldsa-native#86.

### Description of changes: 
The output array is of type `int32_t* a`, thus, `uint32_t` aux values
`t0, t1` cause cbmc proofs to fail due to potential overflow.

### Testing:
`./crypto/crypto_test `

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under the terms of the Apache 2.0 license and the ISC license.

Author: manastasova

crypto/fipsmodule/ml_dsa/ml_dsa_ref/poly.c

@@ -372,19 +372,19 @@ static unsigned int rej_eta(ml_dsa_params *params,
     if (params->eta == 2) {
       if(t0 < 15) {
         t0 = t0 - (205*t0 >> 10)*5;
-        a[ctr++] = 2 - t0;
+        a[ctr++] = 2 - (int32_t)t0;
       }
       if(t1 < 15 && ctr < len) {
         t1 = t1 - (205*t1 >> 10)*5;
-        a[ctr++] = 2 - t1;
+        a[ctr++] = 2 - (int32_t)t1;
       }
     }
 
     else if (params->eta == 4) {
       if(t0 < 9)
-        a[ctr++] = 4 - t0;
+        a[ctr++] = 4 - (int32_t)t0;
       if(t1 < 9 && ctr < len)
-        a[ctr++] = 4 - t1;
+        a[ctr++] = 4 - (int32_t)t1;
     }
   }
   return ctr;