Update tomcat Docker tag to v8.5.76

This MR contains the following updates:

Package	Type	Update	Change
tomcat	ironbank-docker	patch	8.5.75-jdk8-openjdk -> 8.5.76-jdk8-openjdk
tomcat		patch	8.5.75 -> 8.5.76
tomcat	stage	patch	8.5.75-jdk8-openjdk -> 8.5.76-jdk8-openjdk

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