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

We exclude testData pattern from copyright scope

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

@@ -0,0 +1,12 @@
+interface Foo {
+    fun foo(): Int
+}
+
+interface Bar {
+    fun bar(): Int
+}
+
+context(Foo, Bar)
+fun test() {
+    <expr>foo() + bar()</expr>
+}