fix(gtffilter): add support for non-Ensembl GTF files.

[kanishkanandhkumar]

Description of Changes

This PR updates modules/nf-core/custom/gtffilter/templates/gtffilter.py to support non-Ensembl GTF annotations (e.g., NCBI/RefSeq, GENCODE, FlyBase, TAIR).

Summary of fixes:

• Header/Comment preservation: Updated parsing to retain lines starting with # without triggering column-count validation errors.
• Flexible transcript_id matching: Replaced strict Ensembl regex (transcript_id "...") with a flexible regex pattern to match unquoted, single-quoted, and =-separated attributes (e.g., transcript_id=TX123).
• Top-level gene retention: Ensured top-level gene feature entries are preserved even when they lack a transcript_id attribute.
• Gzip support fix: Fixed tab_delimited() validation so .gtf.gz compressed inputs are properly uncompressed during checking rather than throwing column count errors.

Type of Change

• Bug fix (non-breaking change fixing an issue)
• New feature
• Documentation update

Verification

• Ran nf-core modules lint custom/gtffilter locally (Passed 45/45 tests).
• Verified python script syntax and execution.

[pinin4fjords]

@kanishkanandhkumar - sorry, but this is an nf-core module, so you'll need to propose this change in the nf-core/modules repo, get it merged there, then do nf-core modules update ... for this module in your rnaseq copy before you PR here.

Be sure you've joined the nf-core Slack, you can ask for review on module updates there in the request-review channel there.