lib,test: remove lib/internal/test/unicode.js

Remove lib/internal/test/unicode.js and associated test. When we added
the file and test, only comments in lib had non-ASCII characters. Now,
lib/internal/cli_table.js has non-ASCII characters. Tests that exercise
the `console.table()` therefore fulfill the need to test non-ASCII
characters in built-in modules.

PR-URL: https://github.com/nodejs/node/pull/25298
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/cli_table.js

@@ -4,6 +4,12 @@ const { Buffer } = require('buffer');
 const { removeColors } = require('internal/util');
 const HasOwnProperty = Function.call.bind(Object.prototype.hasOwnProperty);
 
+// The use of Unicode characters below is the only non-comment use of non-ASCII
+// Unicode characters in Node.js built-in modules. If they are ever removed or
+// rewritten with \u escapes, then a test will need to be (re-)added to Node.js
+// core to verify that Unicode characters work in built-ins. Otherwise,
+// consumers using Unicode in _third_party_main.js will run into problems.
+// Refs: https://github.com/nodejs/node/issues/10673
 const tableChars = {
   /* eslint-disable node-core/non-ascii-character */
   middleMiddle: '─',