Update process-collect.nf

[meowcat]

Fixes cases with a single file. Note that this example with cat would still work with a single file, but ls *.fq would not. nextflow-io/nextflow#2410

[pditommaso]

not understanding why ls *.fq is not working for a single file

[keiranmraine]

In the example if only a single input is passed the file is linked into the workspace as .fq, a hidden file as far as bash is concerned which is not available via *.fq.

Two issues:

1. it would be preferable to always include the numeric, but I understand the possible implications of changing that.
2. the example it should include a prefix so that hidden files aren't the default from the example:

process bar {
  echo true
  input:
  file 'in_*.fq' from unzipped_ch.collect()
  """
  cat in_*.fq
  """
}

[keiranmraine]

1. file 'in_*.fq' from unzipped_ch.collect() a single file is file_.fq
2. file 'in_?.fq' from unzipped_ch.collect() a single file is file_1.fq

(2) is certainly more consistent and obvious for the example