Dockerfile: disable pip cache in deployment

[pjonsson]

Tell pip to not write the cache when in the deployment image.

Also disable the version check on the remaining uses of pip, this saves some time since it avoids a HTTP request on startup.

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📚 Documentation preview 📚: https://datacube-explorer--589.org.readthedocs.build/en/589/

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 86.32%. Comparing base (aa0d9f3) to head (5bbb147). Report is 25 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #589 +/- ## =========================================== + Coverage 86.29% 86.32% +0.03% =========================================== Files 26 26 Lines 3451 3466 +15 =========================================== + Hits 2978 2992 +14 - Misses 473 474 +1 ```

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