clusterssh: make Perl 5.28 default branch

See: https://trac.macports.org/ticket/58361

sysutils/clusterssh/Portfile

@@ -6,7 +6,7 @@ PortGroup           perl5 1.0
 perl5.require_variant   yes
 perl5.conflict_variants yes
 perl5.branches          5.26 5.28
-perl5.default_branch    5.26
+perl5.default_branch    5.28
 perl5.create_variants   ${perl5.branches}
 
 # since variants are set to conflict (only one can be installed at a time)
@@ -15,7 +15,7 @@ perl5.link_binaries_suffix
 
 name                clusterssh
 perl5.setup         App-ClusterSSH v4.13.2
-revision            2
+revision            3
 platforms           darwin
 categories          sysutils
 license             {Artistic-1 GPL}