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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/partialRawBuilder/simpleFunction.kt

@@ -0,0 +1,16 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+// FUNCTION: foo
+
+package test
+
+fun bar(): Int {
+    return -1
+}
+
+fun foo(): Int {
+    return 0
+}