Add help for GKE

Signed-off-by: Xiang Dai <764524258@qq.com>

docs/troubleshooting.md

@@ -24,7 +24,7 @@ This can have several reasons:
   - Detect this by turning on debug logging and then look for `dropping target, no labels` or `ignoring target` messages.
 - Promtail cannot find the location of your log files. Check that the scrape_configs contains valid path setting for finding the logs in your worker nodes.
 - Your pods are running but not with the labels Promtail is expecting. Check the Promtail scape_configs.
-- Now default scape_configs not work for kubernetes 1.14 and above, if you use 1.14 or above version, need update scape_config from
+- Now default scape_configs not work for original kubernetes 1.14+ and GKE 1.12+, if you use matched version, need update scape_config from
 ```
         - replacement: /var/log/pods/$1/*.log
           separator: /