Update storage-use-azcopy-s3.md

Change env var using $env, not the set command which is a local variable and won't work.

Author: kjhf

articles/storage/common/storage-use-azcopy-s3.md

@@ -40,7 +40,7 @@ Gather your AWS access key and secret access key, and then set these environment
 
 | Operating system | Command  |
 |--------|-----------|
-| **Windows** | `set AWS_ACCESS_KEY_ID=<access-key>`<br>`set AWS_SECRET_ACCESS_KEY=<secret-access-key>` |
+| **Windows** | `$env:AWS_ACCESS_KEY_ID=<access-key>`<br>`$env:AWS_SECRET_ACCESS_KEY=<secret-access-key>` |
 | **Linux** | `export AWS_ACCESS_KEY_ID=<access-key>`<br>`export AWS_SECRET_ACCESS_KEY=<secret-access-key>`|
 | **macOS** | `export AWS_ACCESS_KEY_ID=<access-key>`<br>`export AWS_SECRET_ACCESS_KEY=<secret-access-key>`|