isisd: remove redundant northbound destroy callbacks
Fixes startup warnings:
```
ISIS: [ZKB8W-3S2Q4][EC
100663330] unneeded 'destroy' callback for '/frr-isisd:isis/instance/segment-routing-srv6/msd/node-msd/max-segs-left'
ISIS: [ZKB8W-3S2Q4][EC
100663330] unneeded 'destroy' callback for '/frr-isisd:isis/instance/segment-routing-srv6/msd/node-msd/max-end-pop'
ISIS: [ZKB8W-3S2Q4][EC
100663330] unneeded 'destroy' callback for '/frr-isisd:isis/instance/segment-routing-srv6/msd/node-msd/max-h-encaps'
ISIS: [ZKB8W-3S2Q4][EC
100663330] unneeded 'destroy' callback for '/frr-isisd:isis/instance/segment-routing-srv6/msd/node-msd/max-end-d'
```
Signed-off-by: Igor Ryzhov <iryzhov@nfware.com>
projects / matthieu / frr.git / commit