fix conf.sample.yml.

conf.sample.yml

@@ -52,7 +52,7 @@
 # Log:
 #   Outputs: 'stderr'           # default: stderr, split by ",", you can append files to Outputs if need. example:'stderr,/tmp/test.log'
 #   RotationEnable: 0           # default: 0
-#   RotationConfigJson: '{}'    # example: '{"maxsize": 100, "maxage": 0, "maxbackups": 0, "localtime": false, "compress": false}'
+#   RotationConfigJSON: '{}'    # example: '{"maxsize": 100, "maxage": 0, "maxbackups": 0, "localtime": false, "compress": false}'
 
 # HttpPort: 36789
 # GrpcPort: 36790