content/static: fix typo in favicon url

Change-Id: I2f91996293e72a167d99822a4b8e024d3c85c6e1
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/326809
Trust: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
Reviewed-by: Julie Qiu <julie@golang.org>

content/static/_base/base.tmpl

@@ -18,7 +18,7 @@
       <meta name="description" content="Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.">
     {{end}}
     <meta class="js-gtmID" data-gtmid="{{.GoogleTagManagerID}}">
-    <link rel="shortcut icon" href="/static/_icon//favicon.ico">
+    <link rel="shortcut icon" href="/static/_icon/favicon.ico">
     <!-- Only load the css reset for non-legacy pages -->
     {{if not .UseSiteWrapper}}
       <link href="/static/_base/reset.css" rel="stylesheet">