[ML] Use gcc 10.3 Docker image for Jupyter Dockerfile

[droberts195]

The base image needs to match what the source code
expects, which is version 19 since #2028 was merged.

[dimitris-athanasiou]

LGTM

[droberts195]

The test failure that led to the test threshold change in 3d3db61 was:

[Exception] - difference{0.0119332} between minRecalls[0][0]{0.85760517799352753} and minRecalls[1][0]{0.84749190938511332} exceeds 1%
 == [File] - CDataFrameUtilsTest.cc
 == [Line] -1493

@tveasey and @valeriy42 the threshold increase is pretty small so I don't think it's a problem but just wanted to flag it for you. I imagine there's some performance improvement in gcc 10.3 that leads to single-threaded and multi-threaded diverging slightly more.

[droberts195]

The latest test failure is detailed in #2033. I don't think that's a problem that's been introduced by this PR - it seems to have wider implications for test reproducibility - so I'll merge as-is and leave #2033 to be investigated separately.