cos_gpu_installer: remove python2 dependency

BUG=b/262049161
TEST=build container and use that image to install drivers on COS images:
cos-master, cos-101, cos-97, cos-93, cos-89

using
```
COS_GPU_INSTALLER=<image> cos-extensions install gpu
&
COS_GPU_INSTALLER=<image> cos-extensions install gpu -- --version=latest
```

Change-Id: I4324d514b7eebd9ab58ac37d5d7b72db7406f64c
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/40095
Cloud-Build: Arnav Kansal <rnv@google.com>
Tested-by: Arnav Kansal <rnv@google.com>
Reviewed-by: Meena Shanmugam <meenashanmugam@google.com>
diff --git a/src/cmd/cos_gpu_installer/Dockerfile b/src/cmd/cos_gpu_installer/Dockerfile
index 5cfcb29..5c92a22 100644
--- a/src/cmd/cos_gpu_installer/Dockerfile
+++ b/src/cmd/cos_gpu_installer/Dockerfile
@@ -14,10 +14,8 @@
 # Install minimal tools needed to build kernel modules.
 RUN apt-get update -qq && \
     apt-get install -y xz-utils kmod git make bc curl ccache \
-    libc6-dev pciutils gcc libelf-dev libssl-dev bison flex keyutils python2.7-minimal zlib1g-dev && \
-    rm -rf /var/lib/apt/lists/* && \
-    # x86_64-cros-linux-gnu-clang depends on /usr/bin/python2
-    ln -s /usr/bin/python2.7 /usr/bin/python2
+    libc6-dev pciutils gcc libelf-dev libssl-dev bison flex keyutils python3-minimal zlib1g-dev && \
+    rm -rf /var/lib/apt/lists/*
 
 ENTRYPOINT ["/cos-gpu-installer"]
 CMD ["install"]