Fix styling in ll sample

Author: dsilhavy

samples/low-latency/testplayer/main.css

@@ -6,6 +6,7 @@ video {
     width: 100%;
     height: auto;
     margin: auto;
+    aspect-ratio: 16 / 9;
 }
 
 #manifest {
@@ -48,4 +49,4 @@ video {
 .btn-success:hover {
     background-color: #007bff !important;
     border-color: #007bff !important;
-}
+}