test: cover mixed-case UTF-8 realpath aliases

Author: icecold009

test/parallel/test-fs-realpath-buffer-encoding.js

@@ -8,7 +8,7 @@ const string_dir = fs.realpathSync(fixtures.fixturesDir);
 const buffer_dir = Buffer.from(string_dir);
 
 const encodings = ['ascii', 'utf8', 'utf16le', 'ucs2',
-                   'base64', 'binary', 'hex', 'UTF8', 'UTF-8'];
+                   'base64', 'binary', 'hex', 'UTF8', 'UTF-8', 'Utf8', 'Utf-8'];
 const expected = {};
 for (const encoding of encodings) {
   expected[encoding] = buffer_dir.toString(encoding);