update node and yarn dependencies within install/upgrade docs

changelogs/unreleased/43720-update-fe-webpack-docs.yml

+---
+title: Update documentation to reflect current minimum required versions of node and
+  yarn
+merge_request: 17706
+author:
+type: other

doc/development/fe_guide/index.md

@@ -14,8 +14,8 @@ support through [webpack][webpack].
 We also utilize [webpack][webpack] to handle the bundling, minification, and
 compression of our assets.
-Working with our frontend assets requires Node (v4.3 or greater) and Yarn
-(v0.17 or greater).  You can find information on how to install these on our
+Working with our frontend assets requires Node (v6.0 or greater) and Yarn
+(v1.2 or greater).  You can find information on how to install these on our
 [installation guide][install].
 [jQuery][jquery] is used throughout the application's JavaScript, with

doc/install/installation.md

@@ -162,13 +162,14 @@ page](https://golang.org/dl).
 ## 4. Node
-Since GitLab 8.17, GitLab requires the use of node >= v4.3.0 to compile
-javascript assets, and yarn >= v0.17.0 to manage javascript dependencies.
-In many distros the versions provided by the official package  repositories
-are out of date, so we'll need to install through the following commands:
-
-    # install node v7.x
-    curl --location https://deb.nodesource.com/setup_7.x | sudo bash -
+Since GitLab 8.17, GitLab requires the use of Node to compile javascript
+assets, and Yarn to manage javascript dependencies. The current minimum
+requirements for these are node >= v6.0.0 and yarn >= v1.2.0. In many distros
+the versions provided by the official package repositories are out of date, so
+we'll need to install through the following commands:
+
+    # install node v8.x
+    curl --location https://deb.nodesource.com/setup_8.x | sudo bash -
     sudo apt-get install -y nodejs
     curl --silent --show-error https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -

doc/update/10.5-to-10.6.md

@@ -56,8 +56,8 @@ sudo gem install bundler --no-ri --no-rdoc
 ### 4. Update Node
-GitLab now runs [webpack](http://webpack.js.org) to compile frontend assets.
-We require a minimum version of node v6.0.0.
+GitLab utilizes [webpack](http://webpack.js.org) to compile frontend assets.
+This requires a minimum version of node v6.0.0.
 You can check which version you are running with `node -v`. If you are running
 a version older than `v6.0.0` you will need to update to a newer version. You
@@ -66,8 +66,8 @@ from source at the nodejs.org website.
 <https://nodejs.org/en/download/>
-Since 8.17, GitLab requires the use of yarn `>= v0.17.0` to manage
-JavaScript dependencies.
+GitLab also requires the use of yarn `>= v1.2.0` to manage JavaScript
+dependencies.
 ```bash
 curl --silent --show-error https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -