Bump UPM to 2.20.7 to fix bugs

The current UPM version shipped with Confluence (2.20) does not display the "Update" button for plugin "Confluence Support Health Check" even though the bundled plugin is 1.1.7 and the available version in Marketplace is 2.0.6. This is impacting the adoption of the Support plugin. This issue may be impacting other plugins as well.

The problem is fixed if I upgrade the UPM to 2.20.7.

Screen shots:

1. UPM does not show that "Update" button in 2.20. Even though Marketplace shows that a new version is available and compatible with 5.9.7.

2. After upgrading the UPM to 2.20.7, it is then able to know that a new version is available.