json: fix typo.

libhb/hb_json.c

@@ -995,7 +995,7 @@ hb_job_t* hb_dict_to_job( hb_handle_t * h, hb_dict_t *dict )
 
     // If both vbitrate and vquality were specified, vbitrate is used;
     // we need to ensure the unused rate contro mode is always set to an
-    // invalid value, as if both values aere valid, behavior is undefined
+    // invalid value, as if both values are valid, behavior is undefined
     // (some encoders first check for a valid vquality, whereas others
     //  check for a valid vbitrate instead)
     if (vbitrate > 0)