doc/user/install-operator-sdk.md: Small fixes
```sh
# Set the release version variable
-RELEASE_VERSION=v0.8.0
+$ RELEASE_VERSION=v0.8.0
# Linux
$ curl -OJL https://github.com/operator-framework/operator-sdk/releases/download/${RELEASE_VERSION}/operator-sdk-${RELEASE_VERSION}-x86_64-linux-gnu
# macOS
@@ -17,9 +17,9 @@ $ curl -OJL https://github.com/operator-framework/operator-sdk/releases/download
```sh
# Linux
-curl -OJL https://github.com/operator-framework/operator-sdk/releases/download/${RELEASE_VERSION}/operator-sdk-${RELEASE_VERSION}-x86_64-linux-gnu.asc
+$ curl -OJL https://github.com/operator-framework/operator-sdk/releases/download/${RELEASE_VERSION}/operator-sdk-${RELEASE_VERSION}-x86_64-linux-gnu.asc
# macOS
-curl -OJL https://github.com/operator-framework/operator-sdk/releases/download/${RELEASE_VERSION}/operator-sdk-${RELEASE_VERSION}-x86_64-apple-darwin.asc
+$ curl -OJL https://github.com/operator-framework/operator-sdk/releases/download/${RELEASE_VERSION}/operator-sdk-${RELEASE_VERSION}-x86_64-apple-darwin.asc
```
To verify a release binary using the provided asc files, place the binary and corresponding asc file into the same directory and use the corresponding command:
