Update README for cos_gpu_installer_v2: cmdline arguments for running cos_gpu_installer_v2

Change-Id: Iaf3401ef27542a98046e20330d77c1d0114a066d
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/31840
Reviewed-by: Rayan Dasoriya <dasoriya@google.com>
Tested-by: Arnav Kansal <rnv@google.com>
Cloud-Build: Arnav Kansal <rnv@google.com>
diff --git a/src/cmd/cos_gpu_installer/README.md b/src/cmd/cos_gpu_installer/README.md
index d04945b..b034c82 100644
--- a/src/cmd/cos_gpu_installer/README.md
+++ b/src/cmd/cos_gpu_installer/README.md
@@ -15,13 +15,13 @@
     --pid=host \
     --volume /dev:/dev \
     --volume /:/root \
-    "gcr.io/cos-cloud/cos-gpu-installer:v2" install
+    "gcr.io/cos-cloud/cos-gpu-installer:<tag>" install "-host-dir=/var/lib/nvidia"
 ```
 
 To see all available flags, run the following command:
 
 ```
-/usr/bin/docker run --rm "gcr.io/cos-cloud/cos-gpu-installer:v2" help
+/usr/bin/docker run --rm "gcr.io/cos-cloud/cos-gpu-installer:<tag>" help
 ```
 
 ## Test