Dockerfile.ubi.rocm: fix build

[dtrifiro]

• move microdnf update in base stage
• bump torch version to 2.5.0.dev20240912+rocm6.1
• get rid of build triton stage: it's installed as part of torch when installing from the amd/rocm6.1 index (https://download.pytorch.org/whl/nightly/rocm6.1)

[RH-steve-grubb]

This fixes a conflict where installing triton resolves to an nvidia package which is clearly wrong.
/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dtrifiro, RH-steve-grubb

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[NickLucche]

good job!

[RH-steve-grubb]

/lgtm

[openshift-ci]

@dtrifiro: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/smoke-test	399c114	link	true	/test smoke-test

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