Duplicate phet ZIM files

[MohitMaliFtechiz]

These two phet ZIM files are same size , same content and ISO code which is return by zim file eng.
https://mirrors.dotsrc.org/kiwix/zim/phet/phet_en-ca_2023-01.zim
https://mirrors.dotsrc.org/kiwix/zim/phet/phet_en-gb_2023-01.zim

Only difference is the file name in my opinion we should not rely on file name rather than metadata and seems like both file are returning same metadata.

[kelson42]

@pavel-karatsiuba To me it sounds logic that they are really similar, because they use almost the same language. But I rediscovered that the metadata Language does not support the country variant... so they have actually the exact same language. I think we should stop for the moment to generate the ZIM files for the languages with Variants. Can you please add a new option --withoutLanguageVariants which basically filter out all the ZIM with language including a Country variant (like en-CA for example).

[pavel-karatsiuba]

I have made PR with changes. But I think we need to make it in a different way.
This is my proposition: #207