netlink: specs: explicitly declare block scalar strings

netlink: specs: explicitly declare block scalar strings

In YAML, it is allowed to declare a scalar strings at the next lines
without explicitly declaring them as a block. Yet, they looks weird, and
can cause issues when ':' or '#' are present.

The modified lines didn't have issues with the special characters, but
it seems better to explicitly declare such blocks as scalar strings to
encourage people to "properly" declare future scalar strings.

The right angle bracket is used with a minus sign to indicate that the
folded style should be used without adding extra newlines. By doing
that, the output is not changed compared to what was done before this
patch.

Suggested-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20250913-net-next-ynl-attr-doc-rst-v3-3-4f06420d87db@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>