docs: update required mako version

The requirement was bumped a while back, but we forgot to update the
docs.

Fixes: ed871af91c ("configure.ac: raise Mako required version to
0.8.0")
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

docs/install.html

@@ -75,7 +75,7 @@ you think you've spotted a bug let developers know by filing a
 Version 2.7 or later should work.
 </li>
 <li><a href="http://www.makotemplates.org/">Python Mako module</a> -
-Python Mako module is required. Version 0.3.4 or later should work.
+Python Mako module is required. Version 0.8.0 or later should work.
 </li>
 <li>lex / yacc - for building the Mesa IR and GLSL compiler.
 <div>