download: remove redundant branch and use intended value for genotyping project name

[grapereader]

Description

There was a redundant, unreachable branch for the "pedigree" column in GenotypingPlateLayout.pm. Judging from the git history, the first reachable "pedigree" branch is the intended, faster method. I removed the older, unreachable branch.

Also updated the genotyping project name branch to use the $genotyping_project_name variable already defined further up in the function. This was unused and likely the intended value for this column.

Checklist

• Refactoring only
• Documentation only
• Fixture update only
• Bug fix
  • The relevant issue has been closed.
  • Further work is required.
• New feature
  • Relevant tests have been created and run.
  • Data was added to the fixture
    • Data was added via a patch in /t/data/fixture/patches/.
  • User-Facing Change
    • The user manual in /docs has been updated.
  • Any new Perl has been documented using perldoc.
  • Any new JavaScript has been documented using JSDoc.
  • Any new legacy JavaScript has been moved from /js to /js/source/legacy.