ORCA2_ICE_OBS SETTE test is not synchronised
#### Context
- Branches impacted: main
- Reference configuration/test case: ORCA2_ICE_OBS
#### Analysis and fix
The `ORCA2_ICE_OBS` reference configuration is based on `ORCA2_ICE_PISCES`, but [synchronisation targets cfgs/ORCA2_ICE_OBS](https://forge.nemo-ocean.eu/nemo/nemo/-/blob/5df3a4ce5b0a076c247b5440b3182b64c16ea0fc/sette/sette_reference-configurations.sh#L802) which doesn't exist:
```
configuration ./nemo/cfgs/ORCA2_ICE_OBS_ST/EXP00 not synchronised with ./nemo/cfgs/ORCA2_ICE_OBS/EXPREF
```
The synchronisation target should be `cfgs/ORCA2_ICE_PISCES`:
```diff
# syncronisation if target directory/file exist (not done by makenemo)
clean_config ${CMP_DIR:-${CONFIG_DIR0}}/${SETTE_CONFIG}
- sync_config ${CONFIG_DIR0}/${config} ${CMP_DIR:-${CONFIG_DIR0}}/${SETTE_CONFIG}
+ sync_config ${CONFIG_DIR0}/ORCA2_ICE_PISCES ${CMP_DIR:-${CONFIG_DIR0}}/${SETTE_CONFIG}
```
issue