Renamed ServerRegistry to UpstreamRegistry

[dmartinol]

Forgot this change in previous #2567

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.84%. Comparing base (8ce0337) to head (0508992).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2607   +/-   ##
=======================================
  Coverage   55.84%   55.84%           
=======================================
  Files         312      312           
  Lines       29541    29541           
=======================================
  Hits        16496    16496           
  Misses      11603    11603           
  Partials     1442     1442           

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