docs: remove html comments in protoc docs

[constantoine]

Remove HTML comments in the middle of the MarkDown template because docusaurus rejects them.

Related to #1431.

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
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  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[constantoine]

Hi again, I did this PR because apparently during the docs build, docusaurus crashed, see herepipeline

[vinckr]

Hey @constantoine

I already took a look as well woops.
I think we can leave the comments, it works like I did it here:
#1436

[constantoine]

Hi @vinckr

Woops. No problem, your solution seems better anyway because it also fix auto-closing tags :)