Fix the paragraph separation issue in the documentation

[ashtum]

Fixes #2792

[cppalliance-bot]

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[ashtum]

This breaks some of the new comment blocks because the authors have been relying on the fact that paragraphs in the comment block will not separate in the generated HTML pages.

Like:

I'll fix them as part of this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a0a8035) 93.01% compared to head (e6dcacf) 93.04%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2793      +/-   ##
===========================================
+ Coverage    93.01%   93.04%   +0.02%     
===========================================
  Files          178      178              
  Lines        13688    13688              
===========================================
+ Hits         12732    12736       +4     
+ Misses         956      952       -4     

Files	Coverage Δ
include/boost/beast/websocket/stream.hpp	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

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[cppalliance-bot]

An automated preview of the documentation is available at https://2793.beastdocs.prtest.cppalliance.org/libs/beast/doc/html/index.html