[BugFix] Use correct python3 binary in Docker.ppc64le entrypoint (#9492)

Signed-off-by: Varad Ahirwadkar <varad.ahirwadkar1@ibm.com>

Dockerfile.ppc64le

@@ -33,4 +33,4 @@ WORKDIR /workspace/
 
 RUN ln -s /workspace/vllm/tests && ln -s /workspace/vllm/examples && ln -s /workspace/vllm/benchmarks
 
-ENTRYPOINT ["python3", "-m", "vllm.entrypoints.openai.api_server"]
+ENTRYPOINT ["/opt/conda/bin/python3", "-m", "vllm.entrypoints.openai.api_server"]