Clean up currently available lexicons

[optilete]

@botswanabugs

Please could Si lozi and Silozi be combined. Si Lozi is wrong and Silozi is correct.

Si lozi = Silozi

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und
https://en.wikipedia.org/wiki/ISO_639:u

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synonyms = {
“Aou 4 Letter Codes” => [“Aou 4 Letter Codes”],