Anton Tolchanov cf8948da5f net/routetable: increase route limit used by the test
I was running all tests while preparing a recent stable release, and
this was failing because my computer is connected to a fairly large
tailnet.

```
--- FAIL: TestGetRouteTable (0.01s)
    routetable_linux_test.go:32: expected at least one default route;
    ...
```

```
$ ip route show table 52  | wc -l
1051
```

Updates #cleanup

Signed-off-by: Anton Tolchanov <anton@tailscale.com>
2024-03-14 16:10:40 +00:00
..
2024-03-06 20:22:20 -05:00