MINOR: h3: remove unused return value on decode_qcs

This should fix 1470806 coverity report from github issue #1550.
diff --git a/src/h3.c b/src/h3.c
index 7cecb5d..5f2757f 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -284,9 +284,6 @@
 	}
 
 	return 0;
-
- fail:
-	return -1;
 }
 
 /* Parse a SETTINGS frame which must not be truncated with <flen> as length from