chore: rebrand Nix to Lix when it makes sense

Here's my guide so far:

$ rg '((?!(recursive).*) Nix
(?!(daemon|store|expression|Rocks!|Packages|language|derivation|archive|account|user|sandbox|flake).*))'
-g '!doc/' --pcre2

All items from this query have been tackled. For the documentation side:
that's for https://git.lix.systems/lix-project/lix/issues/162.

Additionally, all remaining references to github.com/NixOS/nix which
were not relevant were also replaced.

Fixes: https://git.lix.systems/lix-project/lix/issues/148.
Fixes: https://git.lix.systems/lix-project/lix/issues/162.
Change-Id: Ib3451fae5cb8ab8cd9ac9e4e4551284ee6794545
Signed-off-by: Raito Bezarius <raito@lix.systems>

src/libstore/daemon.cc

@@ -243,7 +243,7 @@ struct ClientSettings
                 } else if (name == settings.pluginFiles.name) {
                     if (tokenizeString<Paths>(value) != settings.pluginFiles.get())
                         warn("Ignoring the client-specified plugin-files.\n"
-                             "The client specifying plugins to the daemon never made sense, and was removed in Nix >=2.14.");
+                             "The client specifying plugins to the daemon never made sense, and was removed in Nix.");
                 }
                 else if (trusted
                     || name == settings.buildTimeout.name