[transmission] Fixed icon URL in Chart.yml

[bikram990]

Description of the change

Fixes icon url for tranmission chart

Benefits

Tranmission icon will be visible in apps like kubeapps

Possible drawbacks

NA

Applicable issues NA

Additional information

NA

Checklist

• [X] Title of the PR starts with chart name (e.g. [home-assistant])
• [X] Chart version bumped in Chart.yaml according to semver.
• [X] Chart artifacthub.io/changes changelog annotation has been updated in Chart.yaml. See Artifact Hub documentation for more info.