Release Requirement: Update link to the User Guide under [Help] menu

[thao-do]

Please describe the problem that needs to be solved by this feature
Current text and link for the User Guide is incorrect

How important is this feature to you? (Software team will re-prioritize all tickets based on current workload)
Critical

Describe the solution you'd like
Update text from "Tutorial" to "User Guide"
Update link from "allencell.org/..." to the final GitHub page link