OS-784 Bug: fix delegatee wrong deletion

[Rekard0]

Description

Task ID: OS-784

For QA: https://app.satsuma.xyz/subgraphs/750/versions/5531 query:

{
  tokenVotingMembers(where: {plugin: "0x72b1d7ce9748adb10ea7dbd5f9e0456995b02e05"} ) {
    address
    balance
    votingPower
      delegatee {
        address
      }
      delegators {
        address
        balance  
      }
    } 
}

Type of change

See the framework lifecylce in packages/contracts/docs/framework-lifecycle to decide what kind of change this pull request is.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] I have selected the correct base branch.
• [x] I have performed a self-review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] My changes generate no new warnings.
• [ ] Any dependent changes have been merged and published in downstream modules.
• [ ] I ran all tests with success and extended them if necessary.
• [x] I have updated the CHANGELOG.md file in the root folder.
• [ ] I have updated the DEPLOYMENT_CHECKLIST file in the root folder.
• [ ] I have updated the UPDATE_CHECKLIST file in the root folder.