lab2 - nginx image with 1.7.9 tag is no longer supported

Step 8 in lab 2 suggests to update the image in the deployment to `nginx:1.7.9`. This image is no longer supported on Docker hub.

The most recent version is 1.23 with 1.22 being the latest stable version.

Obviously not a huge issue but the devil is in the details.

Thank you for the labs and guidance!