Disable MIVisionX OpenCV example

[zichguan-amd]

Motivation

MIVisionX is no longer built with OpenCV support enabled on non-ubuntu distros.

Technical Details

Disabled opencv_orb and update README.

Test Plan

Test Result

Added/Updated documentation?

• Yes
• No, does not apply to this PR.

Included Visual Studio files?

• Yes
• No, does not apply to this PR.

Submission Checklist

• New examples contain proper CMake and Make files.
• I have updated relevant CI workflows and the new examples are being built and tested in CI.
• Check and guard against unsupported ASICs if relevant dependent libraries have limited support.
• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.