Revert "nix: put builtin in scope when needed"

I don't know where I got this anti-pattern. It makes the LSP unable to
figure out which bindings are unbound

nix/custom/hiosevka/default.nix

@@ -2,7 +2,6 @@
 let
   pname = "hiosevka";
 in
-with builtins;
 (iosevka.overrideAttrs (_: { inherit pname; })).override {
   set = pname;
   /* Guide: https://github.com/be5invis/Iosevka/blob/main/doc/custom-build.md
@@ -10,5 +9,5 @@ with builtins;
      Use `term` spacing to avoid dashed arrow issue
      https://github.com/ryanoasis/nerd-fonts/issues/1018
   */
-  privateBuildPlan = readFile ./buildplan.toml;
+  privateBuildPlan = builtins.readFile ./buildplan.toml;
 }

nix/custom/mkNerdFont.nix

@@ -8,7 +8,6 @@
   extraArgs ? [ ],
   useDefaultsArgs ? true,
 }:
-with builtins;
 stdenvNoCC.mkDerivation {
   /* Credits:
      https://github.com/NixOS/nixpkgs/issues/44329#issuecomment-1231189572
@@ -26,10 +25,10 @@ stdenvNoCC.mkDerivation {
 
   buildPhase =
     let
-      args = concatStringsSep " " extraArgs;
+      args = builtins.concatStringsSep " " extraArgs;
       defArgs =
         if useDefaultsArgs then
-          concatStringsSep " " [
+          builtins.concatStringsSep " " [
             "--careful"
             "--complete"
             "--quiet"