Perl module Privileges::Drop Portfile Fails to Build on Azure

[Steven Smith]

> Add the needed dependencies so that that does not happen.

Everything in PR https://github.com/macports/macports-ports/pull/5482 <https://github.com/macports/macports-ports/pull/5482> is working now except for the remaining issue that one azure build fails because of some issue with perl building the new port `p5-privileges-drop` on `p5.26`, in spite of explicitly specifying `p5.28-*` per @mf2k's review. I don't know how to address this.

See https://paste.z0k.xyz/1179fe812f10:
```
Executing:  cd "/opt/local/var/macports/build/_Users_vsts_agent_2.158.0_work_1_s_perl_p5-privileges-drop/p5.26-privileges-drop/work/Privileges-Drop-1.03" && /opt/local/bin/perl5.26 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang" 
DEBUG: system:  cd "/opt/local/var/macports/build/_Users_vsts_agent_2.158.0_work_1_s_perl_p5-privileges-drop/p5.26-privileges-drop/work/Privileges-Drop-1.03" && /opt/local/bin/perl5.26 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang" 
sh: /opt/local/bin/perl5.26: No such file or directory
Command failed:  cd "/opt/local/var/macports/build/_Users_vsts_agent_2.158.0_work_1_s_perl_p5-privileges-drop/p5.26-privileges-drop/work/Privileges-Drop-1.03" && /opt/local/bin/perl5.26 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang" 
Exit code: 127
```

I was just copying and pasting from an existing perl Portfile, which has:
```
perl5.branches      5.26 5.28
```

Should I just delete the `5.26` part? Is there some other issue?
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