Change value of MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE

Change the value of the error MBEDTLS_ERR_AES_FEATURE_UNAVAILABLE to
0x0023 to ensure the errors in the AES module are all in a continuous
range.
diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 8dfeb62..5fffb0d 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -52,7 +52,7 @@
  * GCM       2  0x0012-0x0014
  * BLOWFISH  2  0x0016-0x0018
  * THREADING 3  0x001A-0x001E
- * AES       2  0x0020-0x0022   0x006E-0x006E
+ * AES       2  0x0020-0x0022   0x0023-0x0023
  * CAMELLIA  2  0x0024-0x0026
  * XTEA      1  0x0028-0x0028
  * BASE64    2  0x002A-0x002C