nix: fish: removed sourcing completion hack

nix/home/_/fish/default.nix

@@ -20,22 +20,12 @@
           (builtins.concatStringsSep "\n")
           (s: s + "\n")
         ];
-
-      source_completions =
-        cs:
-        lib.trivial.pipe cs [
-          (map (c: "source ${c}/share/fish/vendor_completions.d/*.fish"))
-          (builtins.concatStringsSep "\n")
-          (s: s + "\n")
-        ];
     in
     {
       enable = true;
 
       shellInit =
         readConfig "shellInit"
-        # Source packages that are not linked
-        + source_completions config.fish.extraCompletions
         # Just in case $PATH is broken, add them in an idempotent fashion
         + add_paths (
           [