use Optional.of() instead ofNullable() in "opt" postfix template when expression is not null

java/java-tests/testData/codeInsight/template/postfix/templates/opt/notNullMethodCall.java

@@ -0,0 +1,12 @@
+import org.jetbrains.annotations.NotNull;
+
+class Test {
+  @NotNull
+  String foo() {
+    return "";
+  }
+
+  void m() {
+    foo().opt<caret>
+  }
+}

java/java-tests/testData/codeInsight/template/postfix/templates/opt/notNullMethodCall_after.java

@@ -0,0 +1,12 @@
+import org.jetbrains.annotations.NotNull;
+
+class Test {
+  @NotNull
+  String foo() {
+    return "";
+  }
+
+  void m() {
+      java.util.Optional.of(foo())
+  }
+}