yamllint: fix all yamllint brackets errors

Fix all brackets errors detected by yamllint:

yamllint -f parsable -c .yamllint $( find -regex '.*\.y[a]*ml' ) | \
  grep '(brackets)'

Default config is to have no spaces inside brackets, changed few
documentation strings as well that refered to lists even though the
linter does not care about those.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>