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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/getOrBuildFir/declarations/ktij24730.kt

@@ -0,0 +1,7 @@
+fun <T : Any, Z> createTuple(a: T, b: Z&Any): Pair<T, Z&Any> {
+    return Pair(a, b)
+}
+
+fun main()
+    var (<expr>val1</expr>, val2) = createTuple<String, Int?>("a", 1)
+}