[example] Invalid example indentation in beta

[ssssota]

Hello! I found a typo in example.

artemis/example/graphbrainz/build.yaml

Lines 13 to 21 in e029be1

	scalar_mapping:
	- graphql_type: Date
	dart_type: DateTime
	use_custom_parser: true
	- graphql_type: Time
	dart_type: DateTime
	use_custom_parser: true
	- graphql_type: DiscID
	dart_type: String

Invalid indentation at L14.

This commit is in 03c8efa

[vasilich6107]

It seems that L14 is correct
Invalid all other lines

[vasilich6107]

Fixed