Update quay.io/projectquay/clair Docker tag to v4.7.3

This MR contains the following updates:

Package	Type	Update	Change
quay.io/projectquay/clair		patch	4.7.2 -> 4.7.3
quay.io/projectquay/clair	ironbank-docker	patch	4.7.2 -> 4.7.3
quay.io/projectquay/clair	stage	patch	4.7.2 -> 4.7.3

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