Update instance statistics docs images

After merging with analytics, the images related to instance
statistics require an update to refelct being under the
analytics sidebar and nav shortcut.

doc/user/instance_statistics/dev_ops_score.md

@@ -16,7 +16,7 @@ of top-performing instances based on [usage ping data](../admin_area/settings/us
 collected. Your score is compared to the lead score of each feature and then expressed as a percentage at the bottom of said feature.
 Your overall index score is an average of all your feature score percentages - this percentage value is presented above all the of features on the page.
 
-![DevOps Score](img/dev_ops_score.png)
+![DevOps Score](img/dev_ops_score_v12_6.png)
 
 The page also provides helpful links to articles and GitLab docs, to help you
 improve your scores.

doc/user/instance_statistics/index.md

@@ -8,7 +8,7 @@ They are accessible to all users by default (GitLab admins can restrict its
 visibility in the [admin area](../admin_area/settings/usage_statistics.md)),
 and can be accessed via the top bar.
 
-![Instance Statistics button](img/instance_statistics_button.png)
+![Analytics button](img/instance_statistics_button_v12_6.png)
 
 There are two kinds of statistics: