`main` branch that is not default

[mashehu]

Description of the bug

Hi,

Just saw that you have a main branch but use master as a default.
This breaks some of the nf-core pipelinehealth checks, so I would recommend to delete main (it seems to be outdated) or to switch to using it.

[d4straub]

Thanks for making me aware. I seem to lack the permission though, will ask in nf-core slack.

[d4straub]

Done, thanks!