fix indentation
fix indentation

[skip ci]
nlbdev/nordic-epub3-dtbook-migrator,nlbdev/nordic-epub3-dtbook-migrator,mtmse/nordic-epub3-dtbook-migrator,mtmse/nordic-epub3-dtbook-migrator,mtmse/nordic-epub3-dtbook-migrator,nlbdev/nordic-epub3-dtbook-migrator,mtmse/nordic-epub3-dtbook-migrator,nlbdev/nordic-epub3-dtbook-migrator