chore: Bump version to 5.12.20

[rb-union]

Bump version to 5.12.20 PR:

• https://github.com/linuxdeepin/deepin-screen-recorder/pull/459
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/465
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/466
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/467
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/468
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/469
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/470
• https://github.com/linuxdeepin/deepin-screen-recorder/pull/471

Log: Bump version to 5.12.20

[github-actions[bot]]

TAG Bot

TAG: 5.12.20 EXISTED: no DISTRIBUTION: unstable

[rb-union]

/review @starhcq @pengfeixx

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: rb-union, starhcq

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files: - **[debian/deepin/OWNERS](https://github.com/linuxdeepin/deepin-screen-recorder/blob/release/eagle/debian/deepin/OWNERS)** Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[myk1343]

[是否满足兼容性要求] y [是否满足commit提交规范] y [是否满足编码规范] y [review结论] pass [fail原因] n/a

[rb-union]

/merge