correct invalid yaml indentation

Signed-off-by: Guillaume Lours <[email protected]>

.github/stale.yml

@@ -43,7 +43,7 @@ closeComment: >
 limitPerRun: 30
 
 # Limit to only `issues` or `pulls`
- only: issues
+only: issues
 
 # Optionally, specify configuration settings that are specific to just 'issues' or 'pulls':
 # pulls: