Remove double install in index.html.

Author: simi

index.html

@@ -92,7 +92,7 @@ <h2><a id="installation">Installation</a></h2>
         <p>If you are running Linux or Unix you'll need to have a C compiler
             installed so the extension can be built when it is installed. If you
             are running Windows, then you should install the Windows specific gem
-            or install install <a href="https://rubyinstaller.org/add-ons/devkit.html">devkit</a>.</p>
+            or install <a href="https://rubyinstaller.org/add-ons/devkit.html">devkit</a>.</p>
         <p>ruby-prof requires Ruby 2.7.0 or higher.</p>
         <p><strong>!!!WARNING!!!</strong></p>