Bump Python container from 3.11 to 3.14 in SPLIT_PEPTIDES and VARIANT_SPLIT

[jonasscheid]

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
• Make sure your code lints (nf-core pipelines lint).
• Ensure the test suite passes (nf-test test).
• Check for unexpected warnings in debug mode (nextflow run . -profile debug,test,docker --outdir <OUTDIR>).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.

Description of changes

Bumps the biocontainers/python container tag from 3.11 to 3.14 in SPLIT_PEPTIDES and VARIANT_SPLIT modules. These are the only two modules using the bare Python container. Addresses CI failures where quay.io/biocontainers/python:3.11 returned 502 errors (older tags are less reliably cached on quay.io).

Updated all test snapshots to reflect the new Python version (3.11.10 → 3.14.3).

Test plan

• All test snapshots updated for new Python version in SPLIT_PEPTIDES
• CI nf-test pipeline tests