modify README.md in each step webpart.

samples/todo-webpart-sample/src/webparts/todo-step-1/README.md

@@ -1,11 +1,3 @@
 ## Todo sample web part step 1
 
 In this step, we create an empty React web part using Yeoman SharePoint Generator.
-
-## How to build
-
-```bash
-npm install
-gulp serve
-gulp package-solution
-```

samples/todo-webpart-sample/src/webparts/todo-step-2/README.md

@@ -1,11 +1,3 @@
 ## Todo sample web part step 2
 
 In this step, we add the React components and a mock data provider for todo web part.
-
-## How to build
-
-```bash
-npm install
-gulp serve
-gulp package-solution
-```

samples/todo-webpart-sample/src/webparts/todo-step-3/README.md

@@ -4,11 +4,3 @@ In this step, we add a data provider that could interact with current SharePoint
 task lists and CRUD task items.
 
 We also add codes to use framework's property pane to configure the todo web part's properties.
-
-## How to build
-
-```bash
-npm install
-gulp serve
-gulp package-solution
-```

samples/todo-webpart-sample/src/webparts/todo-step-4/README.md

@@ -1,12 +1,5 @@
 ## Todo sample web part step 4
 
 In this step, we add the SharePoint feature xml to the todo-webpart-sample project. It will create a
-default Tasks list (DefaultTodoList) when we deploy the solution package.
-
-## How to build
-
-```bash
-npm install
-gulp serve
-gulp package-solution
-```
+default Tasks list (DefaultTodoList) when we deploy the solution package. Use `gulp package-solution`
+to generate the package and deploy it.