README.md -> URI typo

[telatin]

I found a minor problem in the README while setting up nf-core/mag for offline use:

in the cat_db section, this URI is not working for me (and if the * was intended, is causing a md format change):

Database for taxonomic classification of metagenome assembled genomes (default: none). E.g. "<tbb.bio.uu.nl/bastiaan/CAT*prepare/CAT_prepare_20190108.tar.gz>"

For me, this URI worked:

Database for taxonomic classification of metagenome assembled genomes (default: none). E.g. "<http://tbb.bio.uu.nl/bastiaan/CAT_prepare/CAT_prepare_20190108.tar.gz>"

[skrakau]

Thanks for reporting @telatin !