Clarify upload expectations for BM 1 to 4

[tkphd]

This PR adapts the clarified BM1 upload instructions for BM2 to BM4. The remaining specifications have reasonably clear instructions already.

[review-notebook-app[bot]]

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[pfhub]

@tkphd, the new version of the PFHub website is available at https://random-cat-1511.surge.sh

[tkphd]

... some of the Jekyll templating didn't go through on my local make, @wd15 please work your magic :smile:

[pfhub]

@tkphd, the new version of the PFHub website is available at https://random-cat-1511.surge.sh

[wd15]

This all looks great. Just one thing, could you remove notebooks 1 and 4 from this PR as they don't have any real changes (just white space and python versions)? Thanks.

[tkphd]

Dropped BM1 and BM4+; probably need to regenerate everything again.

[pfhub]

@tkphd, the new version of the PFHub website is available at https://random-cat-1511.surge.sh