[MRG] Update DB links in docs

[luizirber]

I used the OSF links in the last commit, but I can revert it and use the S3 links instead (the first commit here does that).

Connected to #1036 , but still not providing a catalog (as discussed in #1005)

Checklist

• Is it mergeable?
• make test Did it pass the tests?
• make coverage Is the new code covered?
• Did it change the command-line interface? Only additions are allowed
  without a major version increment. Changing file formats also requires a
  major version number increment.
• Was a spellchecker run on the source code and documentation after
  changes were made?

[codecov]

Codecov Report

Merging #1084 into master will increase coverage by 9.10%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1084      +/-   ##
==========================================
+ Coverage   83.86%   92.96%   +9.10%     
==========================================
  Files          98       74      -24     
  Lines        9108     5787    -3321     
==========================================
- Hits         7638     5380    -2258     
+ Misses       1470      407    -1063     

Flag	Coverage Δ
#rusttests	?

Impacted Files	Coverage Δ
src/core/tests/minhash.rs
src/core/src/index/bigsi.rs
src/core/src/cmd.rs
src/core/src/index/sbt/mhbt.rs
src/core/src/index/sbt/mod.rs
src/core/src/ffi/nodegraph.rs
src/core/src/index/linear.rs
src/core/src/ffi/minhash.rs
src/core/src/index/search.rs
src/core/src/signature.rs
... and 14 more

---

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[ctb]

I think the s3 link download would be faster, right?

I'd like to add the catalogs as well as a link to the top level osf project at https://osf.io/t3fqa/, I think. Working on generating the almeida etc catalogs.

[ctb]

the manifests are now up on osf.io, in OSF storage.

[ctb]

I think this is ready for review & merge @luizirber