Consistent usage of the words related to BorgBackup (Borg)

In order to avoid confusions between the name of the program itself (BorgBackup and Borg in short) and the backups managed by BorgBackup, the official full name should be preferred where possible, minding capitalization.

- Borg or borg → BorgBackup
- Borg backup(s) → BorgBackup (if it means the program) / backups with BorgBackup (if it means the backups managed by the program)

Based on https://www.borgbackup.org/

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

CHANGELOG.md

@@ -1021,9 +1021,9 @@ You need to **update your roles** (`just roles` or `make roles`) regardless of w
 
 **TLDR**: the `matrix-backup-borg` role is now included from another repository. Some variables have been renamed. All functionality remains intact.
 
-Thanks to [moan0s](https://github.com/moan0s), the `matrix-backup-borg` role (which configures [Borg backups](docs/configuring-playbook-backup-borg.md)) has been extracted from the playbook and now lives in its [own repository](https://github.com/mother-of-all-self-hosting/ansible-role-backup_borg). This makes it possible to easily use it in other Ansible playbooks and will become part of [nextcloud-docker-ansible-deploy](https://github.com/spantaleev/nextcloud-docker-ansible-deploy) soon.
+Thanks to [moan0s](https://github.com/moan0s), the `matrix-backup-borg` role (which configures [BorgBackup](docs/configuring-playbook-backup-borg.md)) has been extracted from the playbook and now lives in its [own repository](https://github.com/mother-of-all-self-hosting/ansible-role-backup_borg). This makes it possible to easily use it in other Ansible playbooks and will become part of [nextcloud-docker-ansible-deploy](https://github.com/spantaleev/nextcloud-docker-ansible-deploy) soon.
 
-You need to **update your roles** (`just roles` or `make roles`) regardless of whether you're enabling Borg backup functionality or not. If you're making use of Borg backups via this playbook, you will need to update variable references in your `vars.yml` file (`matrix_backup_borg_` -> `backup_borg_`).
+You need to **update your roles** (`just roles` or `make roles`) regardless of whether you're enabling Borg's backup functionality or not. If you're making use of BorgBackup via this playbook, you will need to update variable references in your `vars.yml` file (`matrix_backup_borg_` -> `backup_borg_`).
 
 
 # 2023-02-12
@@ -1775,11 +1775,11 @@ See our [Setting up matrix-registration-bot](docs/configuring-playbook-bot-matri
 
 # 2022-04-19
 
-## Borg backup support
+## BorgBackup support
 
 Thanks to [Aine](https://gitlab.com/etke.cc) of [etke.cc](https://etke.cc/), the playbook can now set up [Borg](https://www.borgbackup.org/) backups with [borgmatic](https://torsion.org/borgmatic/) of your Matrix server.
 
-See our [Setting up borg backup](docs/configuring-playbook-backup-borg.md) documentation to get started.
+See our [Setting up BorgBackup](docs/configuring-playbook-backup-borg.md) documentation to get started.
 
 
 ## (Compatibility Break) Upgrading to Synapse v1.57 on setups using workers may require manual action