docs: update bitbucket server example version (renovatebot#37198)

Signed-off-by: portly-halicore-76 <170707699+portly-halicore-76@users.noreply.github.com>

Author: portly-halicore-76

lib/modules/platform/bitbucket-server/readme.md

@@ -35,7 +35,7 @@ In line with their instructions, the following commands bring up a new server:
 
 ```
 docker volume create --name bitbucketVolume
-docker run -v bitbucketVolume:/var/atlassian/application-data/bitbucket --name="bitbucket" -d -p 7990:7990 -p 7999:7999 atlassian/bitbucket-server:5.12.3
+docker run -v bitbucketVolume:/var/atlassian/application-data/bitbucket --name="bitbucket" -d -p 7990:7990 -p 7999:7999 atlassian/bitbucket-server:8.9.6
 ```
 
 Once it's running and initialized, the quickest way to testing with Renovate is: