[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/redeclarations/RedeclarationInMultiFile.fir.kt

@@ -0,0 +1,9 @@
+// FILE: a.kt
+val a : Int = 1
+fun f() {
+}
+
+// FILE: b.kt
+val a : Int = 1
+fun f() {
+}