fix: remove invalid event loop interest bump

[guybedford]

There are two problems with this event loop interest management for the new blob StreamTask implementation:

1. I'm not seeing where non-cancelled stream tasks are getting their interest decremented
2. Event loop interest is purely about the request / response lifecycle requirements and not arbitrary immediate tracking

//cc @andreiltd

[guybedford]

Strangely the WPT cases are passing here but failed for me locally. Will need some further investigation before landing.

[guybedford]

Can confirm the WPT are passing for me locally so it was a local build issue. In this case this should be okay to land as-is.