Fix tests: "infix modifier required" and "operator modifier required" errors

compiler/testData/codegen/boxWithStdlib/lazyCodegen/increment.kt

@@ -10,7 +10,7 @@ class A(val p: Int) {
 
     var prop = this
 
-    fun inc(): A {
+    operator fun inc(): A {
         return A(p+1)
     }
 

compiler/testData/codegen/boxWithStdlib/lazyCodegen/optimizations/noOptimization.kt

@@ -3,12 +3,12 @@ class B
 
 var holder = 0
 
-fun A.not(): A {
+operator fun A.not(): A {
     holder++
     return this;
 }
 
-fun B.not(): Boolean {
+operator fun B.not(): Boolean {
     holder++
     return false;
 }