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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/getOrBuildFir/wholeDeclaration/localProperty.txt

@@ -0,0 +1,12 @@
+KT element: KtProperty
+FIR element: FirPropertyImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+[ResolvedTo(BODY_RESOLVE)] lval x: R|kotlin/String| = String()
+
+FIR FILE:
+FILE: [ResolvedTo(IMPORTS)] localProperty.kt
+    public final [ResolvedTo(BODY_RESOLVE)] fun y(): R|kotlin/Unit| {
+        [ResolvedTo(BODY_RESOLVE)] lval x: R|kotlin/String| = String()
+    }