CI: Only skip pushing OCI images, not the whole building workflow

[amotl]

Problem

Skipping the whole OCI building workflow here has the consequence that we can't compare build times on patches like GH-211.

influxio/.github/workflows/oci.yml

Lines 70 to 73 in ea69274

	oci:
	needs: build_and_test
	runs-on: ubuntu-latest
	if: ${{ ! (startsWith(github.actor, 'dependabot') || github.event.pull_request.head.repo.fork ) }}

Solution

On the "Build and push image" step, use the push: true attribute to reflect if just the image pushing step should be skipped.