[MRG] change rebase-strategy to disabled for rust dependencies

[ctb]

Our Rust dependency updates from dependabot sit around for a while and are often not something I can evaluate. As they loiter, however, they are updated with every PR into latest. This PR (hopefully) changes that behavior so that the PRs will remain and can be evaluated and updated at a time of our choosing, without triggering lots of PR updates every time something new is merged into latest.

rebase-strategy docs

[codecov]

Codecov Report

Merging #2142 (94758f1) into latest (7900a28) will increase coverage by 7.38%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           latest    #2142      +/-   ##
==========================================
+ Coverage   84.31%   91.70%   +7.38%     
==========================================
  Files         130       99      -31     
  Lines       15293    11017    -4276     
  Branches     2167     2167              
==========================================
- Hits        12895    10103    -2792     
+ Misses       2095      611    -1484     
  Partials      303      303              

Flag	Coverage Δ
python	91.70% <ø> (ø)
rust	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/core/src/sketch/nodegraph.rs
src/core/src/signature.rs
src/core/src/sketch/minhash.rs
src/core/src/index/sbt/mod.rs
src/core/src/storage.rs
src/core/src/ffi/cmd/compute.rs
src/core/src/index/search.rs
src/core/src/errors.rs
src/core/src/sketch/hyperloglog/mod.rs
src/core/src/ffi/utils.rs
... and 21 more

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