Fix warning uncovered by scan-build.

```
src/ciphers/aes/aesni.c:150:7: warning: Value stored to 'temp' is never read [deadcode.DeadStores]
  150 |       temp = temp_invert(rk);
      |       ^      ~~~~~~~~~~~~~~~
1 warning generated.
```

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

Author: sjaeckel

src/ciphers/aes/aesni.c

@@ -147,7 +147,6 @@ int aesni_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_
    for (i = 1; i < skey->rijndael.Nr; i++) {
       rrk -= 4;
       rk += 4;
-      temp = temp_invert(rk);
       *((__m128i*) rk) = temp_invert(rrk);
    }