Remove job token on completion

What does this MR do and why?

Related to #349877

It removes the job token after job completion because the token is not used after a job finishes and it's getting too expensive to maintain. In one year, the size of the index for this column has doubled in size:

# Now

List of relations
 Schema |                Name                | Type  |  Owner  |   Table   |  Size  | Description 
--------+------------------------------------+-------+---------+-----------+--------+-------------
 public | index_ci_builds_on_token_encrypted | index | joe_309 | ci_builds | 250 GB | 
(1 row)

# 1 year ago:

gitlabhq_production=> \di+ index_ci_builds_on_token_encrypted
                                        List of relations
 Schema |                Name                | Type  | Owner  |   Table   |  Size  | Description
--------+------------------------------------+-------+--------+-----------+--------+-------------
 public | index_ci_builds_on_token_encrypted | index | gitlab | ci_builds | 128 GB |
(1 row)

https://console.postgres.ai/gitlab/gitlab-production-ci/sessions/14196/commands/49793

And for partitioning the ci_builds table we need to add the partition_id column in the index's definition, but it proves too difficult to do due to the amount of data that we need to index.

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