doc: fix color of linked code blocks
doc: fix color of linked code blocks

Links nested in backticks were not visually distinguishable before, this
fixes them.

PR-URL: https://github.com/nodejs/node/pull/4068
Reviewed-By: Roman Reiss <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@silverwind.io>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node