Fix issue template to ask for iotedge check without --output json (…

…Azure#1337)

a72a95f added a section for
`iotedge check --output json` output, but `--output json` is not in 1.0.7
(5bf5324).

This commit changes it to ask for just `iotedge check` until 1.0.8 is released.

Ref: Azure#1324

.github/ISSUE_TEMPLATE.md

@@ -27,12 +27,12 @@ Need Support?
 
 ## Context (Environment)
 
-### Output of `iotedge check --output json`
+### Output of `iotedge check`
 
 <details>
 <summary>Click here</summary>
 
-```json
+```
 // Paste here
 ```
 </details>