lib: converted element to lowercase in tty.js

Converted the first element "Eterm" in TERM_ENVS array to "eterm"

PR-URL: https://github.com/nodejs/node/pull/26121
Fixes: https://github.com/nodejs/node/issues/26077
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>

lib/internal/tty.js

@@ -37,7 +37,7 @@ const COLORS_16m = 24;
 // distribution of this file, with or without modification, are permitted
 // provided the copyright notice and this notice are preserved.
 const TERM_ENVS = [
-  'Eterm',
+  'eterm',
   'cons25',
   'console',
   'cygwin',