[Test] Underscored instruction_move_before.

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

Author: nate-chandler

lib/SIL/IR/SILInstruction.cpp

@@ -126,7 +126,7 @@ void SILInstruction::moveBefore(SILInstruction *Later) {
 }
 
 namespace swift::test {
-FunctionTest MoveBeforeTest("instruction-move-before",
+FunctionTest MoveBeforeTest("instruction_move_before",
                             [](auto &function, auto &arguments, auto &test) {
                               auto *inst = arguments.takeInstruction();
                               auto *other = arguments.takeInstruction();

test/SILOptimizer/address_lowering_preprocessed.sil

@@ -27,7 +27,7 @@ bb0(%t : @owned $T, %box : $*Box<T>):
   // The destroy_value appears first in the textual SIL in order to be first in
   // the use list.  Before running AddressLowering, it's sunk to after the
   // end_access.
-  specify_test "instruction-move-before @instruction @instruction[+5]"
+  specify_test "instruction_move_before @instruction @instruction[+5]"
   destroy_value %t : $T
   %copy = copy_value %t : $T
   %field_addr = struct_element_addr %box : $*Box<T>, #Box._value