Update maven Docker tag to v3.8.4

This MR contains the following updates:

Package	Type	Update	Change
maven	ironbank-docker	patch	3.8.3-openjdk-8 -> 3.8.4-openjdk-8
maven		patch	3.8.3 -> 3.8.4
maven	stage	patch	3.8.3-openjdk-8 -> 3.8.4-openjdk-8

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