Use correct notation variable input for GitHub Actions

[apupier]

to fix main branch

Description

avoids this error:

 GitHub.DistributedTask.ObjectTemplating.TemplateValidationException: The template is not valid. /home/runner/work/camel/camel/./.github/actions/incremental-build/action.yaml (Line: 58, Col: 15): Unrecognized named-value: 'artifact-upload-suffix'. Located at position 1 within expression: artifact-upload-suffix,/home/runner/work/camel/camel/./.github/actions/incremental-build/action.yaml (Line: 59, Col: 15): Unrecognized named-value: 'artifact-upload-suffix'. Located at position 1 within expression: artifact-upload-suffix

https://github.com/apache/camel/actions/runs/9365595243/job/25781118249?pr=14329#step:9:3

follow-up to #14339

Target

• I checked that the commit is targeting the correct branch (note that Camel 3 uses camel-3.x, whereas Camel 4 uses the main branch)

Tracking

• If this is a large change, bug fix, or code improvement, I checked there is a JIRA issue filed for the change (usually before you start working on it).

Apache Camel coding standards and style

• I checked that each commit in the pull request has a meaningful subject line and body.

• I have run mvn clean install -DskipTests locally and I have committed all auto-generated changes