fix link

Author: homm

docs/index.html

@@ -385,7 +385,7 @@ <h2 id="blur">Gaussian Blur</h2>
             For most implementations this is true.
             But in 2011 Mathematical Image Analysis Group
             from Saarland University
-            <a href="http://www.mia.uni-saarland.de/Publications/gwosdek-ssvm11.pdf">
+            <a href="https://www.mia.uni-saarland.de/Publications/gwosdek-ssvm11.pdf">
                 proved</a>
             that Gaussian blur can be very closely approximated by
             series of extended box filters.