build: fixing matrix strategy for image provenance

[rsoberano-ld]

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[rsoberano-ld]

images_and_digests should look like a JSON array of objects with image and digest keys:

[{"image":"launchdarkly/ld-relay","digest":"sha256:abbeec99b023cd040fa89b3c30335fd123680a20a6abdff023eb1f23d65217e9"},{"image":"launchdarkly/ld-relay","digest":"sha256:abbeec99b023cd040fa89b3c30335fd123680a20a6abdff023eb1f23d65217e9"},{"image":"launchdarkly/ld-relay","digest":"sha256:abbeec99b023cd040fa89b3c30335fd123680a20a6abdff023eb1f23d65217e9"},{"image":"launchdarkly/ld-relay","digest":"sha256:abbeec99b023cd040fa89b3c30335fd123680a20a6abdff023eb1f23d65217e9"},{"image":"launchdarkly/ld-relay","digest":"sha256:abbeec99b023cd040fa89b3c30335fd123680a20a6abdff023eb1f23d65217e9"},{"image":"launchdarkly/ld-relay","digest":"sha256:abbeec99b023cd040fa89b3c30335fd123680a20a6abdff023eb1f23d65217e9"},{"image":"launchdarkly/ld-relay","digest":"sha256:ae50b3993d45ffcec26a602abbec7d4fc6f0859d7efaf8786d547d7e9f2fba47"},{"image":"launchdarkly/ld-relay","digest":"sha256:ae50b3993d45ffcec26a602abbec7d4fc6f0859d7efaf8786d547d7e9f2fba47"},{"image":"launchdarkly/ld-relay","digest":"sha256:ae50b3993d45ffcec26a602abbec7d4fc6f0859d7efaf8786d547d7e9f2fba47"},{"image":"launchdarkly/ld-relay","digest":"sha256:c6f2c654806e8adad6e0f98ab326517b02ce13e6ffb385e6d2537dade1be13c4"},{"image":"launchdarkly/ld-relay","digest":"sha256:c6f2c654806e8adad6e0f98ab326517b02ce13e6ffb385e6d2537dade1be13c4"},{"image":"launchdarkly/ld-relay","digest":"sha256:c6f2c654806e8adad6e0f98ab326517b02ce13e6ffb385e6d2537dade1be13c4"}]

The matrix.images_and_digests reference should feed that array one object at a time, and we should hopefully be able to then reference the .image and .digest property from each individual object