Docker fix 1: base image and root for apt-get

Author: qianl-nv

docker/Dockerfile.isaaclab_arena

@@ -1,7 +1,10 @@
-ARG BASE_IMAGE=nvcr.io/nvidia/isaac-sim:5.0.0
+ARG BASE_IMAGE=nvcr.io/nvidia/isaac-sim:5.1.0
 
 FROM ${BASE_IMAGE}
 
+# Set user to root (Isaac Sim base image defaults to non-root user)
+USER root
+
 # GR00T Policy Build Arguments, these are only used if INSTALL_GROOT is true
 ARG INSTALL_GROOT=false
 ARG GROOT_DEPS_GROUP=base
@@ -23,9 +26,6 @@ RUN apt-get update && apt-get install -y \
   sudo \
   python3-pip
 
-# Update pip to the latest version
-RUN pip3 install --upgrade pip
-
 ################################
 # Install Isaac Lab
 ################################