Update CHANGELOG.md for 13.4.0+ce.0

[ci skip]

changelogs/unreleased/nhxnguyen-5454.yml

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-title: Fix missing gitlab-geo.conf when initiating replication
-merge_request: 4556
-author:
-type: fixed

changelogs/unreleased/nhxnguyen-5575.yml

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-title: 'Update replicate-geo-database to support PostgreSQL 12'
-merge_request: 4495
-author:
-type: changed

changelogs/unreleased/nhxnguyen-legacy-attributes.yml

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-title: 'Address TODOs for removing legacy attribute support'
-merge_request: 4533
-author:
-type: other

changelogs/unreleased/prometheus-external-labels-configuration.yml

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-title: Allow Prometheus external_labels to be configured
-merge_request: 4494
-author: Chris Weyl @rsrchboy
-type: changed

changelogs/unreleased/sh-add-azure-blob-credentials.yml

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-title: Add Azure Blob Storage configuration
-merge_request: 4505
-author:
-type: added

changelogs/unreleased/sh-add-sidekiq-exporter-log-config.yml

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-title: Add option to enable Sidekiq Exporter logs
-merge_request: 4573
-author:
-type: changed

changelogs/unreleased/smh-auto-reconciliation.yml

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-title: Add Praefect reconciliation config options
-merge_request: 4571
-author:
-type: added

changelogs/unreleased/update-postgresql-to-11-9.yml

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-title: Update PostgreSQL 11 from 11.7 to 11.9
-merge_request: 4545
-author: Takuya Noguchi
-type: security

changelogs/unreleased/update-postgresql-to-12-4.yml

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-title: Update PostgreSQL 12 from 12.3 to 12.4
-merge_request: 4546
-author: Takuya Noguchi
-type: security

changelogs/unreleased/update-python-3-7-9.yml

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-title: Update Python to 3.7.9
-merge_request: 4544
-author: Takuya Noguchi
-type: security

changelogs/unreleased/wc-praefect-tls-move.yml

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-title: Move TLS below Prometheus in Praefect config
-merge_request: 4575
-author:
-type: fixed

changelogs/unreleased/zxjinn-master-patch-80410.yml

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-title: Remove stub_status => on from nginx status on gitlab.rb config file
-merge_request: 4500
-author: Kelvin Jasperson
-type: fixed