Remove unused variables in gloo/test/transport_test.cc

Summary:
LLVM-15 has a warning `-Wunused-but-set-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]]`, mostly in cases where the variable _is_ used, but, eg, in an `assert` statement that isn't present in production code.

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Reviewed By: bunnypak, dmm-fb

Differential Revision: D53011655

fbshipit-source-id: fc7d556051fa9373d4e70d901b7ed5481ca3b29a

Author: r-barnes

gloo/test/transport_test.cc

@@ -166,7 +166,6 @@ TEST_P(TransportMultiProcTest, IoTimeouts) {
 TEST_P(TransportMultiProcTest, UnboundIoErrors) {
   const auto processCount = std::get<0>(GetParam());
   const auto sleepMs = std::get<2>(GetParam());
-  const auto mode = std::get<3>(GetParam());
   const auto transport = std::get<4>(GetParam());
 
   spawnAsync(transport, processCount, [&](std::shared_ptr<Context> context) {
@@ -214,7 +213,6 @@ TEST_P(TransportMultiProcTest, UnboundIoErrors) {
 TEST_P(TransportMultiProcTest, UnboundIoTimeout) {
   const auto processCount = std::get<0>(GetParam());
   const auto sleepMs = std::get<2>(GetParam());
-  const auto mode = std::get<3>(GetParam());
   const auto transport = std::get<4>(GetParam());
 
   spawnAsync(transport, processCount, [&](std::shared_ptr<Context> context) {
@@ -266,7 +264,6 @@ TEST_P(TransportMultiProcTest, UnboundIoTimeout) {
 TEST_P(TransportMultiProcTest, UnboundIoTimeoutOverride) {
   const auto processCount = std::get<0>(GetParam());
   const auto sleepMs = std::get<2>(GetParam());
-  const auto mode = std::get<3>(GetParam());
   const auto transport = std::get<4>(GetParam());
 
   // Use lower timeout than default and pass directly to waitSend/waitRecv.