Update nucypher-core dependency to 0.16.0 and relock dependencies

[derekpierre]

Type of PR:

• Bugfix
• Feature
• Documentation
• Other

Required reviews:

• 1
• 2
• 3

What this does:

High-level idea of the changes introduced in this PR.
List relevant API changes (if any), as well as related PRs and issues.

Issues fixed/closed:

• Fixes #...

Why it's needed:

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E.g., if this PR addresses a nucypher/productdev issue, let reviewers know!

Notes for reviewers:

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.15%. Comparing base (500167b) to head (65ea830).

Additional details and impacted files

@@             Coverage Diff              @@
##           development     #109   +/-   ##
============================================
  Coverage        91.15%   91.15%           
============================================
  Files               18       18           
  Lines              995      995           
============================================
  Hits               907      907           
  Misses              88       88           

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