Your branch filter is in the wrong place. When you’re using workflows the branch filter needs to go into your workflows declaration. You can find the relevant section of the docs here.
Note Workflows will ignore job-level branching. If you use job-level branching and later add workflows, you must remove the branching at the job level and instead declare it in the workflows section of your config.yml, as follows:
You can try something like:
You’ll need to include it in each job until the workflow level filtering feature is implemented.