docs: https all the links \o/

Most of them already redirected to https anyway, so we might as well
avoid the redirection and the security implications by linking directly
to the right protocol.

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Brian Paul <brianp@vmware.com>
diff --git a/docs/shading.html b/docs/shading.html
index e44035a..a28c5b3 100644
--- a/docs/shading.html
+++ b/docs/shading.html
@@ -18,7 +18,7 @@
 
 <p>
 This page describes the features and status of Mesa's support for the
-<a href="http://opengl.org/documentation/glsl/">
+<a href="https://opengl.org/documentation/glsl/">
 OpenGL Shading Language</a>.
 </p>
 
@@ -222,7 +222,7 @@
 </p>
 
 <p>
-The <a href="http://piglit.freedesktop.org/">Piglit</a> project
+The <a href="https://piglit.freedesktop.org/">Piglit</a> project
 has many GLSL tests.
 </p>