Update gatsby project template to address the pipeline failure

Base project template is changed from
https://gitlab.com/pages/gatsby
to
https://gitlab.com/gitlab-org/project-templates/gatsby



Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

changelogs/unreleased/220680-update-gatsby-project-template.yml

+---
+title: Update gatsby project template to address the pipeline failure
+merge_request: 37410
+author: Takuya Noguchi
+type: fixed