chore(js): drop TextEncoder polyfill

Relates-To: elide-dev/elide#1043
Signed-off-by: Sam Gammon <sam@elide.ventures>

elide/runtime/js/polyfills/polyfills.js

@@ -15,4 +15,3 @@ import "./abort-controller.js";
 import "./buffer.js";
 import "./once.js";
 import "./readable-stream.mjs";
-import "./textencoder.js";