Remove unused-variable in fbpcs/emp_games/lift/pcf2_calculator/test/C…

…alculatorAppTest.cpp

Summary:
LLVM-15 has a warning `-Wunused-variable` which we treat as an error because it's so often diagnostic of a code issue. Unused variables can compromise readability or, worse, performance.

This diff either (a) removes an unused variable and, possibly, it's associated code or (b) qualifies the variable with `[[maybe_unused]]`.

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Reviewed By: meyering

Differential Revision: D64279152

fbpcs/emp_games/lift/pcf2_calculator/test/CalculatorAppTest.cpp

@@ -181,7 +181,6 @@ class CalculatorAppTestFixture
 
     auto [communicationAgentFactory0, communicationAgentFactory1] =
         fbpcf::engine::communication::getSocketAgentFactoryPair(tlsInfo);
-    int epoch = 1546300800;
 
     auto future0 = std::async(
         runUDPInputProcessorWithScheduler<0>,