[Test] Ignore test infrastucture sources in debugging tests

This solves no immediate deficiency, but is a to-do that arose as part
of an ongoing effort to port the old, slightly too restrictive
checkLocalVariableTable tests to the more "functional" debugger
infrastructure.

This just shaves a little bit of overhead off the test expectations
and couples them less tightly to the specifics of the test
infrastructure.

compiler/testData/debug/localVariables/suspend/completion/nonStaticStateMachine.kt

@@ -21,7 +21,6 @@ suspend fun box() {
 // test.kt:4 <init>:
 // test.kt:14 box: $completion:kotlin.coroutines.Continuation=helpers.ResultContinuation
 // test.kt:6 foo1:
-// CoroutineUtil.kt:28 getContext:
 
 // LOCAL VARIABLES JVM
 // test.kt:-1 <init>: