Merge pull request #26036 from yuexiao-wang/add-gcplog

Add the content for Google Cloud Loging driver in index
(cherry picked from commit 48659599cbb4c896e9597e50ae16c087d9dd5ac9)

Signed-off-by: Charles Smith <charles.smith@docker.com>

docs/admin/logging/index.md

@@ -21,3 +21,4 @@ weight=9
 * [Amazon CloudWatch Logs logging driver](awslogs.md)
 * [Splunk logging driver](splunk.md)
 * [ETW logging driver](etwlogs.md)
+* [Google Cloud Logging driver](gcplogs.md)