[rocm-libraries] ROCm/rocm-libraries#8716 (commit 8230b20)

[CK] [Security] remove allow-unauthenticated flag from
 dockerfile (#8716)

## Motivation

Dockerfile uses apt-get install --allow-unauthenticated which disables
APT GPG signature verification, allowing package installation without
cryptographic validation. An attacker who can perform a
man-in-the-middle attack on the build network (via corporate proxy, CI
egress, or compromised mirror) can serve trojaned .deb packages such as
libc6, cmake, or git that become embedded in published ROCm container
images distributed to users.

## Technical Details

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## Test Plan

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## Test Result

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## Submission Checklist

- [ ] Look over the contributing guidelines at
https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.