Review rustdoc of `AdvancedPublicationBuilder::attachment`

[fuzzypixelz]

https://docs.rs/zenoh-ext/latest/zenoh_ext/struct.AdvancedPublicationBuilder.html#method.attachment-1

The rustdoc of the above method states that

Attach user-provided data in key-value format

But there doesn't seem to be a From<M> impl for OptionZBytes where M is a map:

• https://docs.rs/zenoh/1.6.2/zenoh/bytes/struct.OptionZBytes.html#trait-implementations
• https://docs.rs/zenoh/1.6.2/zenoh/bytes/struct.ZBytes.html#trait-implementations

cc @milyin.

To reproduce

N/A

System info

• ref: 1.6.2

[milyin]

This is fixed in #2234 - all mentions of key-value format for attachment were removed, they are very obsolete. Current attachment is just ZBytes, key-value is achieved with z_serialize