test: clarified assert message for test-require-json.js

PR-URL: #16807 Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: matthias-reis

test/parallel/test-require-json.js

@@ -29,5 +29,6 @@ try {
 } catch (err) {
  assert.ok(
  /test[/\\]fixtures[/\\]invalid\.json: Unexpected string/.test(err.message),
- 'require() json error should include path');
+ `require() json error should include path - currently: ${err.message}`
+ );
 }