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

We exclude testData pattern from copyright scope

analysis/low-level-api-fir/testData/getOrBuildFir/calls/compoundAssignOnVar_lhs.txt

@@ -0,0 +1,13 @@
+KT element: KtNameReferenceExpression
+FIR element: FirVariableAssignmentImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+R|<local>/i| = R|<local>/i|.R|kotlin/Int.plus|(Int(1))
+
+FIR FILE:
+FILE: [ResolvedTo(IMPORTS)] compoundAssignOnVar_lhs.kt
+    public final [ResolvedTo(BODY_RESOLVE)] fun test(): R|kotlin/Unit| {
+        [ResolvedTo(BODY_RESOLVE)] lvar i: R|kotlin/Int| = Int(1)
+        R|<local>/i| = R|<local>/i|.R|kotlin/Int.plus|(Int(1))
+    }