[artifactory] fix default value for customIngress so we don't get warnings

[b-dean]

PR Checklist

• CHANGELOG.md updated
• Title of the PR starts with chart name (e.g. [artifactory])

What this PR does / why we need it:

Whenever customIngress is specified, helm gives a warning about merging incompatible types (string and map).

Which issue this PR fixes:

fixes #2020

Special notes for your reviewer:
You can test the change before and after this values.yaml change with:

# before
helm template \
  --set customIngress.foo=bar \
  --set ingress.enabled=true \
  --show-only=templates/ingress.yaml \
  --version 107.111.12 \
  jfrog/artifactory

# after
helm dependency build stable/artifactory
helm template \
  --set customIngress.foo=bar \
  --set ingress.enabled=true \
  --show-only=templates/ingress.yaml \
  ./stable/artifactory

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[oumkale]

Hi @b-dean,

Thank you for this PR. We will review it internally and provide an update once it is released.

[chukka]

@b-dean This will be part of 7.117.x patch this week