MRG: fix clippy warnings about max_value

[ctb]

clippy lints (beta) is throwing lots of errors -

 error: usage of a legacy numeric method
Error:     --> src/core/src/sketch/minhash.rs:1312:20
     |
1312 |             usize::max_value()
     |                    ^^^^^^^^^^^
     |
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#legacy_numeric_constants
help: use the associated constant instead
     |
1312 |             usize::MAX
     |       

ref https://rust-lang.github.io/rust-clippy/master/index.html#/legacy_numeric_constants

This PR fixes max_value() calls to ::MAX.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.24%. Comparing base (13ff236) to head (4529ee5).
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Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3146      +/-   ##
==========================================
+ Coverage   86.62%   92.24%   +5.62%     
==========================================
  Files         136      104      -32     
  Lines       15819    12850    -2969     
  Branches     2713     2713              
==========================================
- Hits        13703    11854    -1849     
+ Misses       1806      686    -1120     
  Partials      310      310              

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