feat(users/sterni/nix): move flow.match to string.match

After all it only matches strings.

Change-Id: I3d2e5221ef43f692de69028e78ed98b6b11f82d1
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2586
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

users/sterni/nix/flow/default.nix

@@ -44,11 +44,9 @@ let
   # TODO(sterni): condf or magic
   # like <nixpkgs/pkgs/build-support/coq/extra-lib.nix>
 
-  match = val: matcher: matcher."${val}";
 
 in {
   inherit
     cond
-    match
     ;
 }