Remove all html tags from the GitHub's anchor tag.

[likejazz]

HTML tags should be removed from the GitHub's anchor tag. See below:

- [Heading test with<sup>HTML tags</sup>](#heading-test-withhtml-tags)
...
# Heading test with<sup>HTML tags</sup>

[likejazz]

@buslov Thanks. When will it be merged?

[buslov]

Waiting for @thlorenz or other contributors approved PR. Merge guide