stub `.gz` linting is too restrictive

[famosab]

Description of the bug

This is the linting error that we get here nf-core/modules#11312. It says that the stub syntax should be echo "" | gzip > but echo | gzip > is equally valid. Please reflect that in the linting.

Also related to #4205

[mashehu]

first need to update the guidelines, then I can update the linting https://nf-co.re/docs/specifications/components/modules/general#stub-gzip-files-must-use-echo-and-pipe 🙂

[famosab]

PR is opened :)