package/dillo: remove trailing slash in _SITE url

Commit f2a862fe60 (package/dillo: move to github) changed the source
site for the Dillo package. This change introduced a trailing slash at
the end of the URL.

This cause an error when running `make show-info` with `BR2_PACKAGE_DILLO=y`:

```
package/dillo/dillo.mk:46: *** DILLO_SITE (https://github.com/dillo-browser/dillo/releases/download/v3.0.5/) cannot have a trailing slash.  Stop.
```

This commit removes the trailing slash.

Signed-off-by: Thomas Perale <thomas.perale@mind.be>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit a3b4ae2eaca9791c7c184e49a04a348dd35185c3)

package/dillo/dillo.mk

@@ -6,7 +6,7 @@
 
 DILLO_VERSION = 3.0.5
 DILLO_SOURCE = dillo-$(DILLO_VERSION).tar.bz2
-DILLO_SITE = https://github.com/dillo-browser/dillo/releases/download/v$(DILLO_VERSION)/
+DILLO_SITE = https://github.com/dillo-browser/dillo/releases/download/v$(DILLO_VERSION)
 DILLO_LICENSE = GPL-3.0+
 DILLO_LICENSE_FILES = COPYING
 # configure.ac gets patched, so autoreconf is necessary