Fix peptide test samplesheet: correct target_sequence filename

The test_design_peptide profile was failing because the samplesheet
referenced a non-existent file '2VSM_target_sequence.fa'. Updated to
use the correct file 'nipah_virus_target_sequence_glycoproteinG.fasta'
which exists in assets/test_data/.

This fixes the NoSuchFileException error when running:
nextflow run . -profile test_design_peptide

Also verified that nanobody and protein test profiles have correct
file references.

Author: FloWuenne

assets/test_data/samplesheet_design_peptide.csv

@@ -1,2 +1,2 @@
 sample_id,design_yaml,structure_files,protocol,num_designs,budget,reuse,target_msa,target_sequence,target_template
-design1_pep,assets/test_data/nipah_peptide_design.yaml,assets/test_data/nipah_virus_Glycoprotein_competition_structure.cif,peptide-anything,3,2,,,assets/test_data/2VSM_target_sequence.fa,
+design1_pep,assets/test_data/nipah_peptide_design.yaml,assets/test_data/nipah_virus_Glycoprotein_competition_structure.cif,peptide-anything,3,2,,,assets/test_data/nipah_virus_target_sequence_glycoproteinG.fasta,