You are not following it though. You are using the wrong library and the wrong library example.
That's because it's incompatible.
The "Adafruit OV7670" you are using is written for the SAMD microcontroller architecture. That "cameratest" example sketch is written for the Adafruit Grand Central board, which uses an ATSAMD51P20 microcontroller. You can't use this code with the Uno, nor with the Arduino Industrial 101 board.
Then why does your screenshot show that you have "Arduino Industrial 101" selected from the Arduino IDE's Tools > Board menu?