chore[lang]: remove sha3 and importlib_metadata imports

[charles-cooper]

since we have pycryptodome as a requirement, the sha3 import is dead. additionally, pysha3 is no longer maintained.

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Commit message

since we have `pycryptodome` as a requirement, the `sha3` import is
dead.  additionally, `pysha3` is no longer maintained.

`importlib.metadata` is no longer provisional as of Python3.10, so we
can remove the backported version.

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License

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[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 92.70%. Comparing base (e4e9d7c) to head (ac9eb6c).
Report is 75 commits behind head on master.

Files with missing lines	Patch %	Lines
vyper/__init__.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4588      +/-   ##
==========================================
+ Coverage   92.68%   92.70%   +0.02%     
==========================================
  Files         123      123              
  Lines       17575    17570       -5     
  Branches     2988     2988              
==========================================
  Hits        16289    16289              
+ Misses        888      883       -5     
  Partials      398      398              

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