update chronograf to 1.7.7-alpine (#10938)

stable/chronograf/Chart.yaml

 name: chronograf
-version: 1.0.0
-appVersion: 1.7
+version: 1.0.1
+appVersion: 1.7.7
 description: Open-source web application written in Go and React.js that provides
   the tools to visualize your monitoring data and easily create alerting and automation
   rules.

stable/chronograf/values.yaml

@@ -2,7 +2,7 @@
 ##
 image:
   repository: "docker.io/chronograf"
-  tag: "1.7-alpine"
+  tag: "1.7.7-alpine"
   pullPolicy: "Always"
 
 ## Specify a service type