Update ukm for modern perl

[kousu]

with perl 5.32.0 trying to use ukm gives:

$ ssh gitolite@localhost ukm
Enter passphrase for key '/home/kousu/.ssh/id_rsa': 
FATAL: Can't use global $_ in "my" at /usr/lib/gitolite/commands/ukm line 296, near "($_"
Execution of /usr/lib/gitolite/commands/ukm aborted due to compilation errors.

This fixes it

$ ssh gitolite@localhost ukm list
Enter passphrase for key '/home/kousu/.ssh/id_rsa': 
Hello alice, you manage the following keys:
fingerprint                                     userid keyid
SHA256:VxHhqhOq5GxpPPUrYMeFMly4Mdc3YlP40qkLX4gr5fI alice  alice