fix local_only_partitions.py

[JoshCu]

fix partitioning edge case with 2 partitions

[jcunningham8@compute001 NGIAB-HPCInfra]$ python test.py ../AWI_16_2863657_007/config/cat-2863657_subset.gpkg 1 .
Number of partitions: 1
Number of catchments: 241
Number of nexus: 122
Max cats per partition: 241
Actual number of partitions:
1
[jcunningham8@compute001 NGIAB-HPCInfra]$ python test.py ../AWI_16_2863657_007/config/cat-2863657_subset.gpkg 10 .
Number of partitions: 10
Number of catchments: 241
Number of nexus: 122
Max cats per partition: 25
Actual number of partitions:
10
[jcunningham8@compute001 NGIAB-HPCInfra]$ python test.py ../AWI_16_2863657_007/config/cat-2863657_subset.gpkg 100 .
Number of partitions: 100
Number of catchments: 241
Number of nexus: 122
Max cats per partition: 5
Actual number of partitions:
100
[jcunningham8@compute001 NGIAB-HPCInfra]$ python test.py ../AWI_16_2863657_007/config/cat-2863657_subset.gpkg 1000 .
Number of partitions: 122
Number of catchments: 241
Number of nexus: 122
Max cats per partition: 5
Actual number of partitions:
122
[jcunningham8@compute001 NGIAB-HPCInfra]$ python test.py ../AWI_16_2863657_007/config/cat-2863657_subset.gpkg 2 .
Number of partitions: 2
Number of catchments: 241
Number of nexus: 122
Max cats per partition: 121
Actual number of partitions:
2

fixes issues in CIROH-UA/NGIAB-HPCInfra#39

[benlee0423]

I will get it tested on Pantarhei, and update it
Thank you for the quick fix.