Invalid assumptions in media-source/mediasource-changetype-util.js

[jyavenard]

https://github.com/web-platform-tests/wpt/blob/3a2402822007826e89a1dc4fd5534977cccd1753/media-source/mediasource-changetype-util.js#L288C5-L288C17

The scripts ensure that 2.1s is the minimum duration of the file and trim it to 2s.

However, many of the files used in testing aren't 2.1s long, they are 2.03s long causing an error.

This check also serves no purpose, the duration of the file is irrelevant in the context of the MediaSource.changeType as all we need to know is if we can change the type of content being appended and making sure the result plays.