Remove Server-sent events in http.markdown

[N1co93]

Proposed change

I noticed that there is a broken link at the http integration: https://www.home-assistant.io/integrations/http/#apis
There is also support for Server-sent events

This link is pointing to https://developers.home-assistant.io/docs/external_api_server_sent_events/ This side was removed with this pull request home-assistant/developers.home-assistant#508

frenck told me in #16114 that the support for "Server-sent events" was removed.

In this pull request I like to delete the old information and broken link from http-integration.

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • I've opened up a PR to add logo's and icons in Brands repository.
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase:
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: Broken link at http integration #16114

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.

[frenck]

Thanks, @N1c093 👍