chore: remove unused counting proxy

[miparnisari]

Description

The proxy stopped emmitting metrics after we removed the middleware 😅 : fd6ca35#diff-6ae9faef9b462443abb234855106fee0b829623efba66a3c0b3217eb5ad9087c

And anyway we can get data from spicedb_datastore_query_latency_count:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.84%. Comparing base (9d4d4b7) to head (bc8203a).
⚠️ Report is 1 commits behind head on main.

❌ Your project status has failed because the head coverage (74.84%) is below the target coverage (75.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2967       +/-   ##
===========================================
+ Coverage   48.86%   74.84%   +25.98%     
===========================================
  Files         431      497       +66     
  Lines       54679    60621     +5942     
===========================================
+ Hits        26714    45365    +18651     
+ Misses      25251    12099    -13152     
- Partials     2714     3157      +443     

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