update angular 8 code example

Example 1: how to update angular version

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      ng update @angular/cli @angular/core

Example 2: update angular

npm uninstall -g @angular-cli
npm install -g @angular/cli@latest

Example 3: angular 8 to 9

First, update to the latest version of 8
ng update @angular/cli@8 @angular/core@8

Then, update to 9
ng update @angular/cli @angular/core