LibMedia: Prefix AK::Duration with AK Namespace

Author: https://github.com/ADKaster
Commit: c1681931ba
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/676
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/trflynn89 ✅

Tests/LibMedia/TestParseMatroska.cpp

@@ -20,6 +20,6 @@ TEST_CASE(master_elements_containing_crc32)
 
     auto iterator = MUST(matroska_reader.create_sample_iterator(video_track));
     MUST(iterator.next_block());
-    MUST(matroska_reader.seek_to_random_access_point(iterator, Duration::from_seconds(7)));
+    MUST(matroska_reader.seek_to_random_access_point(iterator, AK::Duration::from_seconds(7)));
     MUST(iterator.next_block());
 }