Remove error notification from the UpdateCluster command

Description

This PR removes the notify() call from the error case of the UpdateCluster command (same as it had been already done with the CreateCluster)

The error is handled via the errorHandler which takes care of setting the errors in the store

This also avoid displaying an error Flash message, in case of successful dry run (see screenshot below)

[ ] I added tests to new or existing code
[ ] I removed hardcoded strings and used our i18n solution instead (see here)
[ ] I made sure no sensitive info gets logged at any time in the codebase (see here) (e.g. no user info or details, no stacktraces, etc.)
[ ] I checked that infrastructure/update_infrastructure.sh runs without any error
[x] I checked that npm run build builds without any error
[x] I checked that clusters are listed correctly
[x] I checked that a new cluster can be created (config is produced and dry run passes)
[ ] I checked that login and logout work as expected

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