Small JSON-RPC timeout to lower proxygen RAM usage

[dimalit]

Looks like, we had 30 min timeout on socket inactivity. It caused RAM consumption growth under high load by requests.
Tested in stability test with RAM usage monitoring

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.85%. Comparing base (4c87471) to head (108993e).
⚠️ Report is 3312 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1725      +/-   ##
===========================================
- Coverage    45.19%   44.85%   -0.35%     
===========================================
  Files          351      351              
  Lines        51430    51430              
===========================================
- Hits         23245    23069     -176     
- Misses       28185    28361     +176     

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