Set Accept-Language header for all curl requests.

[reitermarkus]

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Homebrew/homebrew-cask#89251 is currently failing because curl without the Accept-Language header is returning a 404 for https://www.minecraft.net/.

I don't think it hurts passing this header to all requests (tried brew fetch with a bunch of formulae and casks).

curl -LI https://www.minecraft.net/ # 404
curl -LI -H 'Accept-Language: en' https://www.minecraft.net/ # 200