noweb: fix nawk binary name

The package `nawk` seems to supply the binary `nawk` not `awk`, not sure if this was always thus, or if this is a new change.
```
$ tree `nix eval -f '<nixpkgs>' --raw nawk`
/nix/store/jji0m1by0nks2pdplk6xpwqq0dz8qy2s-nawk-unstable-2021-02-15
├── bin
│   └── nawk
└── share
    └── man
        └── man1
            └── nawk.1.gz

```

pkgs/development/tools/literate-programming/noweb/default.nix

@@ -57,7 +57,7 @@ lib.fix (noweb: stdenv.mkDerivation rec {
         # NOTE: substituteInPlace breaks Icon binaries, so make sure the script
         #       uses (n)awk before calling.
         if grep -q nawk "$f"; then
-            substituteInPlace "$f" --replace "nawk" "${nawk}/bin/awk"
+            substituteInPlace "$f" --replace "nawk" "${nawk}/bin/nawk"
         fi
     done