fix(coverage): Exclude comment lines from coverage reports

[usualoma]

fixes #25938

I think comments should be excluded from line coverage.

current result

patched result

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

Thanks for the PR @usualoma, it looks good at first glance. We're a bit swamped with Deno 2.0 release ATM, so it might have a couple weeks before we merge it. Thanks!

[bartlomieju]

Note to self: compare how other tools like nyc or istanbul do that. Are the comment lines excluded from the total line count or are they always counted as covered.

[kt3k]

Tested istanbul (via jest). The comment lines seem excluded from total line count.