Fix apache reverse proxy example (#4742)

So that it actually works. See https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxypass



Signed-off-by: Paul Tötterman <paul.totterman@iki.fi>

docs/reverse_proxy.rst

@@ -79,7 +79,7 @@ Let's assume that we expect clients to connect to our server at
           SSLEngine on
           ServerName example.com;
 
-          <Location />
+          <Location /_matrix>
               ProxyPass http://127.0.0.1:8008/_matrix nocanon
               ProxyPassReverse http://127.0.0.1:8008/_matrix
           </Location>