Fix typo in config.json.example
Fix typo in config.json.example

We recently added the new logging option. As it turns out, the new
option was not added correctly, which points out that our current json
linting is **not working**. It throws an error but doesn't break.

This patch fixes the typo in the example. It does not fix the CI part.

Signed-off-by: Sheogorath <1c2647ce2ee8a4ec8e5c8b1b245ca38f94844bab@shivering-isles.com>

hackmdio/hackmd,jackycute/HackMD,hackmdio/hackmd,Yukaii/hackmd,jackycute/HackMD,Yukaii/hackmd,hackmdio/hackmd,jackycute/HackMD,Yukaii/hackmd