[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/topLevelFunction.txt

@@ -0,0 +1,16 @@
+KT element: KtNamedFunction
+FIR element: FirSimpleFunctionImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+public final [ResolvedTo(BODY_RESOLVE)] fun x(): R|kotlin/Unit| {
+    local final [ResolvedTo(BODY_RESOLVE)] fun y(): R|kotlin/String|
+
+}
+
+FIR FILE:
+FILE: [ResolvedTo(IMPORTS)] topLevelFunction.kt
+    public final [ResolvedTo(BODY_RESOLVE)] fun x(): R|kotlin/Unit| {
+        local final [ResolvedTo(BODY_RESOLVE)] fun y(): R|kotlin/String|
+
+    }