bug#64539: Possible issue with GNU sed documentation regarding the -n option

[Ângelo Otávio Nuffer Nunes]

Dear GNU sed maintainers,

I am writing to report a possible issue with the documentation for the `-n`
option in GNU `sed`. According to the documentation available at
https://www.gnu.org/software/sed/manual/html_node/Command_002dLine-Options.html,
the `-n` option should cause `sed` to only produce output when explicitly
told to via the `p` command.

However, based on responses and comments on this Stack Overflow post (
https://stackoverflow.com/questions/76633771/why-does-gnu-sed-print-output-when-using-the-n-option-with-the-a-command/76639116#76639116)
and my own tests, it appears that several other commands, including `=`,
`l`, `r`, `a`, `i`, and `c`, also produce output even when the `-n` option
is used.

I am still learning how to use GNU `sed`, so I may be misunderstanding
something. However, I wanted to bring this to your attention in case there
is an issue with the documentation that needs to be addressed.

Thank you for your time and for all the work you do on GNU `sed`.

Best regards,
Ângelo Nuffer