After opening a Collaborate project, warning in Collaborate window appears that Unity version has changed. Pressing "click here for more details." button opens https://docs.unity3d.com/Manual/UnityCollaborateUpgradeConsiderations.html which gives Error 404 Page not found.

To reproduce:
1. Create a new project
2. Push it to Collaborate
3. Close the project and open it with another Unity version
4. Open Collaborate window and observe the warning
5. Press "click here for more details." button

Expected result: a documentation page is opened
Actual result: Error 404 page not found is opened

Reproduced on: 5.6.4p4 2017.1.3p1 2017.2.1p4 2017.3.1p1 2018.1.0b5 2018.1.0b6
Not reproduced on: 5.5.5p2

Notes: 5.5.5p2 opens https://docs.unity3d.com/540/Documentation/Manual/UnityCollaborateUpgradeConsiderations.html which is working.