build(nginx): update Nginx to UBI9

[ebaron]

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Fixes: cryostatio/cryostat#650

Description of the change:

• Updates the Nginx container to UBI9

Motivation for the change:

• Consistency with the other images

How to manually test:

1. Build/deploy

[ebaron]

/build_test

[ebaron]

/retest

[ebaron]

/build_test

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