Update docker.io/library/caddy Docker tag to v2.7.4

This MR contains the following updates:

Package	Type	Update	Change
docker.io/library/caddy	final	minor	2.6.4-alpine -> 2.7.4-alpine
docker.io/library/caddy	stage	minor	2.6.4-builder-alpine -> 2.7.4-builder-alpine

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