(v6.x backport) doc: fix stylistic issues in api/net.md#11969

aqrln wants to merge 1 commit intonodejs:v6.x-stagingnodejs/node:v6.x-stagingfrom

aqrln:pr11786-backport-v6.xaqrln/node:pr11786-backport-v6.xCopy head branch name to clipboard