cf-files: correctly handle duplicate file refs

[itzg]

Reported in Discord

After an container restart I'm hit with this issue:

[mc-image-helper] 19:02:26.734 INFO  : Fabric launcher for minecraft 1.20.1 loader 0.15.10 is already available
[mc-image-helper] 19:02:28.217 INFO  : Downloading /data/mods/Structory_1.20.1_v1.3.2.jar from https://mediafilez.forgecdn.net/files/4630/983/Structory_1.20.1_v1.3.2.jar
[mc-image-helper] 19:02:29.234 ERROR : 'curseforge-files' command failed. Version is 1.38.5
java.lang.IllegalStateException: Duplicate key ModFileIds(modId=667389, fileId=4802504) (attempted merging values CurseForgeFilesManifest.FileEntry(ids=ModFileIds(modId=667389, fileId=4802504), filePath=mods/goblintraders-fabric-1.20.1-1.9.3.jar) and CurseForgeFilesManifest.FileEntry(ids=ModFileIds(modId=667389, fileId=4802504), filePath=mods/goblintraders-fabric-1.20.1-1.9.3.jar))

I noticed that I did have the goblintrader mod specified twice in my config, but it seems that it was running was no issues
I tried to completely remove the mod but I'm still getting the same error