Remove parentObject from proto file

[Shahar-Y]

it's deprecated

[yonatandt]

Do it in the next pull request that will change the file-service proto file.

[yoavrozner]

• Create a new branch from develop.
• Make sure that the parentObject is not in use in the code.
• Remove it from the proto file.
• Regenerate the new proto.
• Run the tests.
• Use bloom rpc to check manually the functionality.
• Update the changelog.md.