fix: remove abortable iterator from muxer #124

Job	Run time
check	1m 11s
test-chrome-webworker	45s
test-node (windows-latest, lts/*)	2m 27s
test-firefox	6m 49s
test-chrome	31s
test-node (ubuntu-latest, lts/*)	22s
test-node (macos-latest, lts/*)	2m 6s
test-firefox-webworker	1m 4s
test-webkit (ubuntu-latest, lts/*)	16s
test-webkit-webworker (ubuntu-latest, lts/*)	11s
test-webkit (macos-latest, lts/*)	1m 42s
test-webkit-webworker (macos-latest, lts/*)	1m 37s
test-electron-main	26s
test-electron-renderer	25s
release	0s
	19m 52s

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