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/int/tests/default.nix

@@ -12,7 +12,6 @@ let
     int
     string
     fun
-    flow
     ;
 
   testBounds = it "checks minBound and maxBound" [
@@ -113,7 +112,7 @@ let
 
   checkShift = { a, b, c, op }@args:
     let
-      f = flow.match op {
+      f = string.match op {
         "<<" = int.bitShiftL;
         ">>" = int.bitShiftR;
       };