[Access] Update model Block REST API Response

[UlyanaAndrukhiv]

issue: onflow/flow-go#6874

Context

In this PR the openAPI was updated:

• the omitempty tag was added to the Expandable field for Block,
• the block_status field was added for Block

[UlyanaAndrukhiv]

The block_status field was introduced in flow-go's model_block.go but was missing here. This addition ensures consistency between the two models.

For reference, the commit where block_status was added to flow-go: commit

[peterargue]

for reference, these are defined here