DOC: Provide correct link for tifffile plugin.

skimage/io/_plugins/tifffile_plugin.py

@@ -3,4 +3,4 @@ try:
 except ImportError:
     raise ImportError("The tifffile module could not be found.\n"
         "It can be obtained at "
-        "<http://www.lfd.uci.edu/~gohlke/code/tifffile.py.html>\n")
+        "<http://www.lfd.uci.edu/~gohlke/code/tifffile.py>\n")