Fix to comment to correct module description

the CTR-DRBG module will now support AES-128 as well as AES-256
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 58b2f25..dbcfb57 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -2027,7 +2027,7 @@
  *
  * Requires: MBEDTLS_AES_C
  *
- * This module provides the CTR_DRBG AES-256 random number generator.
+ * This module provides the CTR_DRBG AES random number generator.
  */
 #define MBEDTLS_CTR_DRBG_C