Merge branch 'fix/PRXS-2730-DeleteFallbackLocales' into 'master'

Вынесена в константу ошибка при удалении языка, который является fallback в Locales API

See merge request perxis/perxis-go!293

pkg/locales/errors.go

@@ -17,4 +17,5 @@ var (
 	ErrDisablePublishingDefaultLocale = errors.New("cannot disable publishing for default locale")
 	ErrSetDefaultLocaleFallback       = errors.New("cannot set fallback for default locale")
 	ErrDeleteDefaultLocale            = errors.New("cannot delete default locale")
+	ErrDeleteFallbackLocale           = errors.New("cannot delete locale that is used as fallback for other locales")
 )