fix(argocd-image-updater): Add webhook port to NetworkPolicy

[william-mateille-citopia]

Closes #3678

I hesitated to create a networkPolicy.create option in the values.yaml (juste like argo-cd helm), but this means either changing the default behavior, or having different default values between helms (since the default if false for argo-cd networkPolicy, but right now argocd-image-updater deploys a NetworkPolicy if the metric server is enabled)

I also don't like very much adding the webhook port to a NetworkPolicy named argocd-image-updater-allow-metrics but I wanted a minimal change, I'm open to better suggestion!

First time contributing to anything open source, I spend way too much time editing those 2 lines to make sure everything's in order

Checklist:

• I have bumped the chart version according to versioning
• I have updated the documentation according to documentation
• I have updated the chart changelog with all the changes that come with this pull request according to changelog.
• Any new values are backwards compatible and/or have sensible default.
• I have signed off all my commits as required by DCO.
• I have created a separate pull request for each chart according to pull requests
• My build is green (troubleshooting builds).

[jmeridth]

@william-mateille-citopia thank you for your contribution. Your initial feelings like this doesn't belong here feel justified but this seems to be the smallest change to allow this to go through. @mkilchhofer @yu-croco @tico24 please take a look and provide opinion. Thank you.

[yu-croco]

Thank you for your contribution. LGTM.