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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/contextCollector/localClass.kt

@@ -0,0 +1,9 @@
+fun test() {
+    class Local {
+        fun foo(): String {
+            <expr>return "foo"</expr>
+        }
+    }
+
+    Local().foo()
+}