Download: Add apptainer to the list of false positve container strings

[MatthiasZepper]

Add apptainer keyword to the list of false positive matches. Bare minimum to possibly support a future apptainer.registry notation in the container specifications ?

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #2353 (d2b8a45) into dev (cdf620e) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head d2b8a45 differs from pull request most recent head 464f2fb. Consider uploading reports for the commit 464f2fb to get more accurate results

@@            Coverage Diff             @@
##              dev    #2353      +/-   ##
==========================================
- Coverage   72.76%   72.75%   -0.02%     
==========================================
  Files          78       78              
  Lines        8889     8889              
==========================================
- Hits         6468     6467       -1     
- Misses       2421     2422       +1     

Impacted Files	Coverage Δ
nf_core/download.py	59.47% <100.00%> (ø)

... and 1 file with indirect coverage changes