Update to Hugo 0.53 and remove all .Site references (#12079)

* Remove all .Site variable references

* Update Hugo version in Travis CI config and Makefile

layouts/docs/docsportal_home.html

@@ -38,7 +38,7 @@
 
       <div class="launch-card">
         <h4>Try Kubernetes</h4>
-        
+
         <p>Follow tutorials to learn how to deploy applications in Kubernetes.</p>
         <br>
         <ul>
@@ -53,7 +53,7 @@
 
       <div class="launch-card">
         <h4>Set up a cluster</h4>
-        
+
         <p>Get Kubernetes running based on your resources and needs.</p>
         <br>
         <ul>
@@ -70,7 +70,7 @@
 
       <div class="launch-card">
         <h4>Learn how to use Kubernetes</h4>
-        
+
         <p>Look up common tasks and how to perform them using a short sequence of steps.</p>
         <br>
         <ul>
@@ -86,7 +86,7 @@
 
       <div class="launch-card">
         <h4>Look up reference information</h4>
-        
+
         <p>Browse terminology, command line syntax, API resource types, and setup tool documentation.</p>
         <br>
         <ul>
@@ -102,7 +102,7 @@
 
       <div class="launch-card">
         <h4>Contribute to the docs</h4>
-        
+
         <p>Anyone can contribute, whether you’re new to the project or you’ve been around a long time.</p>
         <br>
         <ul>
@@ -118,7 +118,7 @@
 
       <div class="launch-card">
         <h4>Download Kubernetes</h4>
-        
+
         <p>If you are installing Kubernetes or upgrading to the newest version, refer to the current release notes.</p>
         <br>
         <ul>
@@ -130,7 +130,7 @@
 
       <div class="launch-card">
         <h4>About the documentation</h4>
-        
+
         <p>This website contains documentation for the current and previous 4 versions of Kubernetes.</p>
         <br>
         <ul>