This has come up a few times in the past couple weeks for this exact Thunderbird package, for example here: Garuda-update fails due to "conflicting files" and here: Error updating system.
The link Kayo posted not only fixes the problem, it also briefly explains why this error sometimes comes up in the first place. It's good information if you are interested in learning more about the mechanics behind your system.
It also has the benefit of being a solution that will work every time; I do not know if the same is true for Bauh, or any other package manager, because I do not know specifically how they are resolving the issue.