test: modernize and correct test-doctool-html.js
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
commit message follows commit guidelines
- Use destructuring when it is appropriate.
- Correct nits in comments.
- Reduce unneeded wrapping with string concatenations when it is cheap diff-wise.
- Diverge similar variables by renaming one of them.