yamllint: fix all yamllint hyphens errors

Fix all hyphens errors detected by yamllint:

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

Default config is only one space after the hyphen.

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