Merge pull request #13206 from Kausheel/kausheel/fix_export_syntax

📖  docs: minor fix for Bash syntax

Author: k8s-ci-robot

docs/book/src/tasks/diagnostics.md

@@ -22,8 +22,8 @@ To continue serving metrics via http the following configuration can be used:
 
 The same can be achieved via clusterctl:
 ```bash
-export CAPI_DIAGNOSTICS_ADDRESS: "localhost:8080"
-export CAPI_INSECURE_DIAGNOSTICS: "true"
+export CAPI_DIAGNOSTICS_ADDRESS="localhost:8080"
+export CAPI_INSECURE_DIAGNOSTICS="true"
 clusterctl init ...
 ```