Use standard std::shared_lock for C++14

[andrey-kashcheev]

While the std::shared_mutex is C++17, the lock implementation was added in C++14

Relates-To: MINOR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.36%. Comparing base (8d13756) to head (8ab287e).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1651      +/-   ##
==========================================
+ Coverage   80.33%   80.36%   +0.03%     
==========================================
  Files         350      350              
  Lines       14039    14041       +2     
  Branches     1515     1516       +1     
==========================================
+ Hits        11278    11284       +6     
+ Misses       2147     2144       -3     
+ Partials      614      613       -1     

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