Makefile: remove trailing '/' from DOCS_URL

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

Makefile

@@ -2,7 +2,7 @@
 
 export GIT_URL=https://github.com/asciimoo/searx
 export SEARX_URL=https://searx.me
-export DOCS_URL=https://asciimoo.github.io/searx/
+export DOCS_URL=https://asciimoo.github.io/searx
 
 PYOBJECTS = searx
 DOC       = docs