The way `(lib.formats.yaml {}).generate` generates YAML is compliant
because on YAML 1.2 spec JSON is a subset of YAML but it bugs people's
minds and can lead to problems with software that is not compatible with
YAML 1.2.
This commit also changes the test of the generation function. Data
validation/typing remains the same.
See #133802.
Signed-off-by: lucasew <lucas59356@gmail.com>
Julien Moutinho