fix: Only abort pipeablestream if not already closed

[rschristian]

Remix/React-Router seems to always call abort() after a short timeout. This reports the following "error":

Error: The render was aborted by the server without a reason.
    at Timeout.abort [as _onTimeout] (file:///home/ryun/Projects/tmp-react-router-preact/node_modules/preact-render-to-string/src/stream-node.js:75:4)
    at listOnTimeout (node:internal/timers:594:17)
    at processTimers (node:internal/timers:529:7)

To my understanding, this is something we can ignore if the stream has already been closed. React does something along these lines too, checking to ensure there's tasks that can be aborted before throwing and cleaning up further.

cc @sbesh91

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🦋 Changeset detected

Latest commit: cdfae86

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
preact-render-to-string	Patch

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[marvinhagemeister]

LGTM