test: disable colors in test-assert-checktag.js

When test/parallel/test-assert-checktag.js is run with a TTY
as stdout, color codes in assertion messages cause the test to
fail. This commit disables colors when stdout is a TTY.

PR-URL: #20695
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-assert-checktag.js

@@ -2,6 +2,12 @@
 require('../common');
 const assert = require('assert');
 
+// Disable colored output to prevent color codes from breaking assertion
+// message comparisons. This should only be an issue when process.stdout
+// is a TTY.
+if (process.stdout.isTTY)
+  process.env.NODE_DISABLE_COLORS = '1';
+
 // Turn off no-restricted-properties because we are testing deepEqual!
 /* eslint-disable no-restricted-properties */