nixos/locate: PRUNE_BIND_MOUNTSFR -> PRUNE_BIND_MOUNTS

PRUNE_BIND_MOUNTSFR seems to be a typo.
The man page only mentions it in a header and further in the paragraph
it is PRUNE_BIND_MOUNTS.

Also breaks plocate which complains about the unknown option.

nixos/modules/misc/locate.nix

@@ -202,7 +202,7 @@ in {
           PRUNEFS="${lib.concatStringsSep " " cfg.pruneFS}"
           PRUNENAMES="${lib.concatStringsSep " " cfg.pruneNames}"
           PRUNEPATHS="${lib.concatStringsSep " " cfg.prunePaths}"
-          PRUNE_BIND_MOUNTSFR="${lib.boolToString cfg.pruneBindMounts}"
+          PRUNE_BIND_MOUNTS="${if cfg.pruneBindMounts then "yes" else "no"}"
         '';
       };
     };