Fix deprecated API usage

Author: Sergey Mashkov

frontend/src/org/jetbrains/demo/thinkter/Login.kt

@@ -19,7 +19,7 @@ class LoginComponent : ReactDOMComponent<UserProps, LoginFormState>() {
     override fun ReactDOMBuilder.render() {
         div {
             form(classes = "pure-form pure-form-stacked") {
-                legEnd { +"Login" }
+                legend { +"Login" }
 
                 fieldSet(classes = "pure-group") {
                     input(type = InputType.text, name = "login") {
@@ -95,4 +95,4 @@ class LoginComponent : ReactDOMComponent<UserProps, LoginFormState>() {
     }
 }
 
-class LoginFormState(var login: String, var password: String, var disabled: Boolean, var errorMessage: String?) : RState
+class LoginFormState(var login: String, var password: String, var disabled: Boolean, var errorMessage: String?) : RState

frontend/src/org/jetbrains/demo/thinkter/NewThoughtComponent.kt

@@ -17,7 +17,7 @@ class NewThoughtComponent : ReactDOMComponent<NewThoughtComponent.Props, NewThou
 
     override fun ReactDOMBuilder.render() {
         form(classes = "pure-form pure-form-stacked") {
-            legEnd {
+            legend {
                 if (props.replyTo == null) {
                     +"New thought"
                 } else {
@@ -80,4 +80,4 @@ class NewThoughtComponent : ReactDOMComponent<NewThoughtComponent.Props, NewThou
 
     class State(var text: String = "", var errorMessage: String? = null) : RState
     class Props(var replyTo: Thought? = null, var replyToUser: User? = null, var showThought: (Thought) -> Unit = {}) : RProps()
-}
+}

frontend/src/org/jetbrains/demo/thinkter/Register.kt

@@ -20,7 +20,7 @@ class RegisterComponent : ReactDOMComponent<UserProps, RegisterFormState>() {
     override fun ReactDOMBuilder.render() {
         div {
             form(classes = "pure-form pure-form-stacked") {
-                legEnd { +"Register" }
+                legend { +"Register" }
 
                 fieldSet(classes = "pure-group") {
                     input(type = InputType.text, name = "login") {
@@ -121,4 +121,4 @@ class RegisterComponent : ReactDOMComponent<UserProps, RegisterFormState>() {
     }
 }
 
-class RegisterFormState(var login: String, var displayName: String, var password: String, var email: String, var errorMessage: String?, var disabled: Boolean) : RState
+class RegisterFormState(var login: String, var displayName: String, var password: String, var email: String, var errorMessage: String?, var disabled: Boolean) : RState