Separate build 41 filter in workshop to allow distinctions between b41 beta and b41 stable

[Its_geno]

When using the Build 41 filter in the workshop, it shows both b41 beta and b41 stable mods. This makes it more difficult to find mods that actually work in the most recent update. Separating the build 41 filter into b41 beta and b41 stable filters would help reduce the difficulty of modding project zomboid, especially for players that are new to project zomboid (a rapidly increasing population of players since the mp update.)