clearInterval instead of clearTimeout in ManifestUpdater.js

[Robloche]

I know most browsers seem to handle clearInterval and clearTimeout the same way but for the sake of clarity, and since the timer is initialized with:
refreshTimer = setTimeout(onRefreshTimer, delay);
I think it should be cleared through clearTimeout.

Actual code:

function stopManifestRefreshTimer() {
        if (refreshTimer !== null) {
            clearInterval(refreshTimer);
            refreshTimer = null;
        }
    }

Source:

dash.js/src/streaming/ManifestUpdater.js

Line 110 in 13745c6

clearInterval(refreshTimer);

[dsilhavy]

Fixed in #3160