remove hardcoded dea-tools in sys.path

[emmaai]

Describe the bug/issue
Noticing that many notebooks got the relative path of dea-tools hardcoded in sys.path. We might want to discourage this as dea-tools is a proper package now. It can be installed either by pip install -e . or pip install dea-tools from pypi. Also might consider to build this in the sandbox image in the future.

Steps to reproduce
Steps to reproduce the behaviour. For example:
N/A
Expected behaviour
N/A

Environment information
What datacube environment are you using?
DEA Sandbox