Big change in quickfix tests: no stupid test data format with "before" and "after" file prefixes

idea/testData/quickfix/override/nothingToOverride/removeParameterTwoTraits.kt

@@ -0,0 +1,11 @@
+// "Change function signature to 'fun f()'" "true"
+trait A {
+    fun f()
+}
+trait B {
+    fun f()
+}
+
+class C : A, B {
+    <caret>override fun f(a: String) {}
+}