Remove conflicting -U option for apk in Dockerfile

[PeterDaveHello]

Proposed changes

The --no-cache option updates the index and avoids temporary files, making -U unnecessary, consistent with the subsequent apk add.

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[GeorginaReeder]

Thanks for your contribution @PeterDaveHello !