[Test] Underscored lexical_destroy_folding.

Use underscores rather than hyphens so that text editors understand the
name as a single word.

Author: nate-chandler

lib/SILOptimizer/Utils/LexicalDestroyFolding.cpp

@@ -812,7 +812,7 @@ namespace swift::test {
 // Dumps:
 // - the function
 static FunctionTest LexicalDestroyFoldingTest(
-    "lexical-destroy-folding", [](auto &function, auto &arguments, auto &test) {
+    "lexical_destroy_folding", [](auto &function, auto &arguments, auto &test) {
       auto *dominanceAnalysis = test.template getAnalysis<DominanceAnalysis>();
       DominanceInfo *domTree = dominanceAnalysis->get(&function);
       auto value = arguments.takeValue();

test/SILOptimizer/lexical_destroy_folding_unit.sil

@@ -24,7 +24,7 @@ sil [ossa] @callee_owned : $@convention(thin) (@owned C) -> ()
 // CHECK-LABEL: } // end sil function 'nofold_two_parallel_owned_uses_one_lexical___scope_ends_before_use'
 sil [ossa] @nofold_two_parallel_owned_uses_one_lexical___scope_ends_before_use : $@convention(thin) (@owned C) -> () {
 entry(%instance : @owned $C):
-  specify_test "lexical-destroy-folding @trace[0]"
+  specify_test "lexical_destroy_folding @trace[0]"
   %copy_2 = copy_value %instance : $C
   %lifetime = begin_borrow [lexical] %instance : $C
   debug_value [trace] %lifetime : $C