"which" is superfluous and it breaks "bitmessagemain --curses"

the word "which" must be removed

src/depends.py

@@ -363,7 +363,7 @@ def check_curses():
     import subprocess
 
     try:
-        subprocess.check_call('which dialog')
+        subprocess.check_call('dialog')
     except subprocess.CalledProcessError:
         logger.error(
             'Curses requires the `dialog` command to be installed as well as'