[LL FIR] rename testdata to testData to avoid copyright generation

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/contextCollector/smartCasts/when.kt

@@ -0,0 +1,14 @@
+interface Foo {
+    fun foo()
+}
+
+interface Bar {
+    fun bar()
+}
+
+fun test(obj: Any) {
+    when (obj) {
+        is Foo -> obj.foo()
+        is Bar -> <expr>obj.bar()</expr>
+    }
+}