bug: pandoc not being installed, fixed

[rbiseck3]

Description

There is no pandoc install file with the aarch64 arch designation and the following portion was never copied over during the last refactor:

if [ "$ARCH" == "aarch64" ]; then
  PANDOC_ARCH="arm64"
else
  PANDOC_ARCH="amd64"
fi

This will now set the arch appropriately when pulling down the pandoc file.