Some fixes can not be reliably detected

[joyeecheung]

nodejs/node#16604

Body HTML is:

<p>Included reference to \'constant time\' in crypto.timingSafeEqual description</p>\n<p><span aria-label="This pull request closes issue #16504." class="issue-keyword tooltipped tooltipped-se">Fixes</span> : <a href="https://github.com/nodejs/node/issues/16504" class="issue-link js-issue-link" data-error-text="Failed to load issue title" data-id="268571876" data-permission-text="Issue title is private" data-url="https://github.com/nodejs/node/issues/16504">#16504</a></p>

Where there is a space before :

[apapirovski]

Also potentially relevant: https://help.github.com/articles/closing-issues-using-keywords/ — that's all the different versions that github supports, meaning a first-time contributor to Node might use one of the other formats.