disable EncodeAPI.Buganizer503197490 w/CONFIG_REALTIME_ONLY

This fixes a failure with that configuration:

```
[ RUN      ] EncodeAPI.Buganizer504317456
test/encode_api_test.cc:2451: Failure
Expected equality of these values:
  aom_codec_enc_config_default(iface, &cfg, 0u)
    Which is: 8
  AOM_CODEC_OK
    Which is: 0
```

Bug: 504317456
Change-Id: Ifdd30648cd87ab2e3c985cd4608a9c24b0042899

test/encode_api_test.cc

diff --git a/test/encode_api_test.cc b/test/encode_api_test.cc
index 70f7c46..6e67964 100644
--- a/test/encode_api_test.cc
+++ b/test/encode_api_test.cc
@@ -2445,6 +2445,7 @@
   ASSERT_EQ(aom_codec_destroy(&codec), AOM_CODEC_OK);
 }
 
+#if !CONFIG_REALTIME_ONLY
 TEST(EncodeAPI, Buganizer504317456) {
   aom_codec_iface_t *iface = aom_codec_av1_cx();
   aom_codec_enc_cfg_t cfg;
@@ -2487,5 +2488,6 @@
   aom_img_free(img);
   ASSERT_EQ(aom_codec_destroy(&enc), AOM_CODEC_OK);
 }
+#endif  // !CONFIG_REALTIME_ONLY
 
 }  // namespace