Improve left nav for Tasks. (#8582)

* Add weights to first three Task sections.

* Add one more weight.

content/en/docs/tasks/tools/_index.md

@@ -1,5 +1,5 @@
 ---
 title: "Install Tools"
-weight: 20
+weight: 10
 ---
 

content/en/docs/tasks/tools/install-kubeadm.md

@@ -1,6 +1,7 @@
 ---
 title: Installing kubeadm
 content_template: templates/task
+weight: 30
 ---
 
 {{% capture overview %}}

content/en/docs/tasks/tools/install-kubectl.md

@@ -4,6 +4,7 @@ reviewers:
 - mikedanese
 title: Install and Set Up kubectl
 content_template: templates/task
+weight: 10
 ---
 
 {{% capture overview %}}

content/en/docs/tasks/tools/install-minikube.md

@@ -1,6 +1,7 @@
 ---
 title: Install Minikube
 content_template: templates/task
+weight: 20
 ---
 
 {{% capture overview %}}