flake: follow tincr lassulus/fixes-rebased
Incident 2026-10-17: radio→styx UDP was blackholed for ~40 min after a
sendto() hit ENETUNREACH; tincd never recovered the UDP path on its own.
The fix is upstream as Mic92/tincr#140.
The fork is rebased onto upstream Mic92/tincr main: 6 of the 8 commits on
lassulus/fixes are upstream now, leaving the tunnel-address gate and the
ENETUNREACH fix on lassulus/fixes-rebased (bfcbbc69).
pkgs/tincr pins the same branch and is what every machine runs (the flake
input only provides barnacle's darwin module), so bump it and its update
script along with the input.