Updating Dockerfile and PGEcore

[nickjhathaway]

Updated dockerfile for new variantstring version; Updated PGEcore for new variantstring, which required changes for other changes to PGEcore including name changes for adding ref seqs via full genome or targeted fasta; updated MLBM test for output change;

PR checklist

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added a new tool - have you followed the pipeline conventions in the contribution docs
• If necessary, also make a PR on the nf-core/plasmodiumdrugres branch on the nf-core/test-datasets repository.
• Make sure your code lints (nf-core pipelines lint).
• Ensure the test suite passes (nextflow run . -profile test,docker --outdir <OUTDIR>).