includes.php: add trailing slashes to generated wiki links
Our wiki instances have an apache proxy running in front of them. By default, the following apache directive is enabled: https://httpd.apache.org/docs/current/mod/mod_dir.html#directoryslash
This will cause a redirect for urls without a trailing slash that
are accessing a directory. In the case of K3s envs, the apache proxy
listens on port 8080 which in production will create a redirection
url like e.g. 49b8d5c4b5.catalyst.wmcloud.org/w
->
49b8d5c4b5.catalyst.wmcloud.org:8080/w/
.
This redirection will fail, as the call to catalyst.wmcloud.org
will have to go again through the external cloud vps web proxy. This
proxy listens on port 80 only.
Adding the trailing slash to the generated wiki urls avoids the redirection and solves the problem
Bug: T373078