chore(issue_template): Add reminder about the gitsync private repo (#1478)

* chore(issue_template): Add reminder about the gitsync private repo

* chore(issue_template): Move reminder to spark product updates

Leaving a hint in the airflow version bumps. Although, it won't be noticable at 0.0.0-dev time.

Author: NickLarsenNZ

.github/ISSUE_TEMPLATE/update-product-airflow.md

@@ -34,6 +34,11 @@ Add/Change/Remove anything that isn't applicable anymore
 - [ ] Ensure prerequisites are up to date (required-external-components.adoc).
 - [ ] Update the version in demos. Add the PR(s) to the list below.
 
+> [!TIP]
+> The tests might fail to pull an image if the spark version is not updated in the private repo as part
+> of the Spark version bumps.
+> This is usually only discoverable after branching, because there are always old versions for 0.0.0-dev.
+
 ## Related Pull Requests
 
 > [!TIP]

.github/ISSUE_TEMPLATE/update-product-spark.md

@@ -34,6 +34,7 @@ Add/Change/Remove anything that isn't applicable anymore
 - [ ] Update other dependencies if applicable (eg: python, jmx_exporter, aws_java_sdk_bundle, etc).
 - [ ] Check other operators (getting_started / kuttl / supported-versions) for usage of the versions. Add the PR(s) to the list below.
 - [ ] Update the version in demos. Add the PR(s) to the list below.
+- [ ] Update the version in the SparkApplication within the [stackable-airflow/dags](https://github.com/stackable-airflow/dags) private repository.
 
 ## Related Pull Requests