Remove response stream disconnected status gate

[joshthoward]

No description provided.

[jclee]

Thanks! This looks good to me, but probably worth keeping in mind that the internal web-socket-proxy test in edgeworker currently covers the behavior difference between the two autogate settings, so it would also need to be updated at the same time as the workerd dependency that removes the conditional behavior. I believe it is simply a matter of merging the versions of the tests with all-autogates and not-all-autogates test results (I think the relevant tests can be found by grepping for RESPONSE_STREAM_DISCONNECTED_STATUS). Let me know if you'd like me to help.

[joshthoward]

The internal PR is passing checks and approved. I am going to go ahead and merge, update the internal PR to point to the merge commit, and then merge the internal PR. Please LMK if that isn't the right process.