Update hygieiadoc/api Docker tag to v3.4.21

This MR contains the following updates:

Package	Type	Update	Change
hygieiadoc/api	ironbank-docker	patch	v3.4.20 -> v3.4.21
hygieiadoc/api		patch	3.4.20 -> v3.4.21
hygieiadoc/api	stage	patch	v3.4.20 -> v3.4.21

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