Fix locale variables in Nix and .envrc

[mdimjasevic]

Some wire-server tests would fail if the locale variables were not set properly. This PR moves setting the LANG variable into .envrc (and also puts LC_ALL there). Furthermore, there is no need to set these variables any more in tools/ormolu.sh.

The C locale is Debian/Ubuntu-specific; it has been removed from the Ormolu script.

See https://sourceware.org/legacy-ml/libc-alpha/2015-02/msg00247.html.

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[mdimjasevic]

@jschaul , hopefully this fixes some test failures you have been observing locally on your machine.

[mdimjasevic]

@jschaul , I just tested this locally and it looks like all the problems you report in https://wearezeta.atlassian.net/browse/SQSERVICES-1552 and https://wearezeta.atlassian.net/browse/SQSERVICES-1553 seem to be addressed by this PR.

[jschaul]

Thank you for the fix! Works for me.