When converting docs from RDoc to Markdown, some label-lists ended up
not rendering properly. This appears to be due to RDoc's Markdown
parser not recognizing label-list labels if the label has additional
markup around it (in this case, bold markers `**`).

Additionally, the markdown label-list was missing newlines between list
items which also caused the label-list to not render correctly.

This commit fixes both of these issues for cases where the RDoc
originally used <b> tags in a label-list label. Since label-list labels
will already be bolded, there is no reason to also use `**` on the
labels.