Change installation example to be consistent with the documentation

docs: https://gohugo.io/getting-started/installing/#install-hugo-with-brew

From this commit: gohugoio/hugoDocs@d4f7985

Signed-off-by: budparr <budparr@gmail.com>

layouts/partials/home-page-sections/installation.html

@@ -16,7 +16,7 @@ <h3 class="f2 black">Install in seconds, build in milliseconds.</h3>
       </div>
       <p class="f6 mid-gray m0 p0 pt3">Mac OS</p>
       <div class="code f6 bg-black light-green lh-copy pv3 ph3 br2 w-100 w-50-ns center mb2 tl">
-        $ brew update && brew install hugo <br />
+        $ brew install hugo <br />
       </div>
       <p class="f6 mid-gray">Windows</p>
       <div class="code f6 bg-black light-green lh-copy pv3 ph3 br2 w-100 w-50-ns center tl">