PSI Pattern Matching: Fix matching of !!

#KT-6021 Fixed

idea/testData/refactoring/extractFunction/duplicates/notNullAssertion.kt

@@ -0,0 +1,12 @@
+// PARAM_TYPES: kotlin.String?, kotlin.Comparable<String>?, kotlin.CharSequence?, kotlin.Any?
+// PARAM_DESCRIPTOR: val s: kotlin.String? defined in foo
+
+// SIBLING:
+fun foo(): Int {
+    val s: String? = ""
+    return if (true) {
+        <selection>s!!.length</selection>
+    } else {
+        s!!.length
+    }
+}

idea/testData/refactoring/extractFunction/duplicates/notNullAssertion.kt.after

@@ -0,0 +1,16 @@
+// PARAM_TYPES: kotlin.String?, kotlin.Comparable<String>?, kotlin.CharSequence?, kotlin.Any?
+// PARAM_DESCRIPTOR: val s: kotlin.String? defined in foo
+
+// SIBLING:
+fun foo(): Int {
+    val s: String? = ""
+    return if (true) {
+        i(s)
+    } else {
+        i(s)
+    }
+}
+
+private fun i(s: String?): Int {
+    return s!!.length
+}