The “solution” (if this should be seen as a problem) seems to be to add a custom css-file as @findmyway pointed out like given here Resizing images in docs - #8 by Tamas_Papp. The entry that needs to be modified is in documenter-light.css
:
code {
background-color: rgba(0, 0, 0, 0.05);
color: #da0b00; /* would need to be removed */
font-size: 0.875em;
font-weight: normal;
padding: 0.1em; }