[doc] Use same style for all code
[doc] Use same style for all code

Currently, highlighted code is much smaller than non-highlighted code.
There's no good reason for that, and looks inconsistent. Remove the
override for highlighted code, making it look the same as
non-highlighted code.

Signed-off-by: Philipp Wagner <5a4b10454c30419e54a1570be358a516ff84bb63@lowrisc.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan