chore: fix MD031 lint error

seeing lint error in https://github.com/runatlantis/atlantis/actions/runs/9196911456/job/25296141721

```
runatlantis.io/docs/server-configuration.md:477 MD031/blanks-around-fences Fenced code blocks should be surrounded by blank lines [Context: "```"]
```

Signed-off-by: Rui Chen <rui@chenrui.dev>

Author: chenrui333

runatlantis.io/docs/server-configuration.md

@@ -475,6 +475,7 @@ and set `--autoplan-modules` to `false`.
   # or
   ATLANTIS_EMOJI_REACTION=thumbsup
   ```
+
   The emoji reaction to use for marking processed comments. Currently supported on Azure DevOps, GitHub and GitLab. If not specified, Atlantis will not use an emoji reaction.
   Defaults to "" (empty string).