nixos/rspamd: Fix enable for locals and overrides

[griff]

Motivation for this change

When implementing #49620 I included an enable option for both the
locals and overrides options but the code writing the files didn't
actually look at enable and so would write the file regardless of its
value. I also set the type to loaOf which should have been attrsOf
since the code was not written to handle the options being lists.

This fixes both of those issues.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.

---

[fpletz]

@GrahamcOfBorg test rspamd.customLuaRules

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: tests.rspamd.customLuaRules

Partial log (click to expand)

machine: exit status 1
syncing
machine: running command: sync
machine: exit status 0
test script finished in 207.28s
cleaning up
killing machine (pid 600)
vde_switch: EOF on stdin, cleaning up and exiting
vde_switch: Could not remove ctl dir '/build/vde1.ctl': Directory not empty
/nix/store/2xnd5ln1q9mnj6xdnzz6z2aq4n2himq5-vm-test-run-rspamd-custom-lua-rules

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Attempted: tests.rspamd.customLuaRules

Partial log (click to expand)

machine: exit status 1
syncing
machine: running command: sync
machine: exit status 0
test script finished in 112.92s
cleaning up
killing machine (pid 631)
vde_switch: EOF on stdin, cleaning up and exiting
vde_switch: Could not remove ctl dir '/build/vde1.ctl': Directory not empty
/nix/store/y9a9n7fm9h6qdakhrfk12w4cgnzf6dc0-vm-test-run-rspamd-custom-lua-rules