Update fluent/fluent-bit Docker tag to v1.5.1

This MR contains the following updates:

Package	Type	Update	Change
fluent/fluent-bit	ironbank-docker	minor	1.4.6 -> 1.5.1
fluent/fluent-bit		minor	1.4.6 -> 1.5.1
fluent/fluent-bit	stage	minor	1.4.6 -> 1.5.1

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