[RELEASE ONLY] Use release torchao version for OpenVINO (#15880)

### Summary
OpenVINO CI is failing on the release branch. We can avoid the build
from source by just using the release ao version installed with
pyproject.toml.

### Test Plan
The [test-openvino-linux /
linux-job](https://github.com/pytorch/executorch/actions/runs/19485963505/job/55768329507?pr=15880#logs)
run is passing on this PR (failing on trunk).

Author: GregoryComer

backends/openvino/scripts/openvino_build.sh

@@ -54,9 +54,6 @@ main() {
         # Build the package
         ./install_executorch.sh --minimal
 
-        # Install torchao
-        pip install third-party/ao
-
     else
         echo "Error: Argument is not valid: $build_type"
         exit 1  # Exit the script with an error code