synchroniser : remove wait for foreground links update

The run function already waits for the command to finish and wheter or
not it actually runs in the background is handled before using & and
nohup.
Furthermore it also appears that this code might be broken.
So there is only one thing to do : remove it

src/unisync/synchroniser.py

@@ -279,12 +279,12 @@ class Synchroniser:
                 link_background_wrapper
                 ]
 
-        link_update_process = subprocess.run(command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        print("Updating links")
-
+        subprocess.run(command,
-        if not background:
+                       stdout=subprocess.DEVNULL,
-            print("Starting links update.")
+                       stderr=subprocess.DEVNULL,
-            link_update_process.wait()
+                       check=False
-            print("Done")
+                       )
 
     def mount_remote_dir(self):
         """Mounts the remote directory to make the local links work.