Revert "Print ps in intervals while the process is running"

This reverts commit 50c6d8d3.

Reason for revert: self argument missing

Original change's description:
> Print ps in intervals while the process is running
> 
> R=​apolito@google.com, ehmaldonado@chromium.org
> 
> Bug: 1074355
> Change-Id: Id2d5c8ca6f27fefb0fe8d769ae2e50dbaaddadbb
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2167221
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Anthony Polito <apolito@google.com>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

TBR=ehmaldonado@chromium.org,apolito@google.com,infra-scoped@luci-project-accounts.iam.gserviceaccount.com,sokcevic@google.com

Change-Id: I3c90576d0c6403f0d2f9119876a400c1380a8e14
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1074355
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2169391Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -117,16 +117,11 @@ class PsPrinter(object):
     self.active = sys.platform.startswith('linux2')
     self.thread = None
 
+  @staticmethod
   def print_pstree():
     """Debugging function used to print "ps auxwwf" for stuck processes."""
-    # Add new line for cleaner output
-    print()
     subprocess.call(['ps', 'auxwwf'])
 
-    # Restart timer, we want to continue printing until the process is
-    # terminated.
-    self.poke()
-
   def poke(self):
     if self.active:
       self.cancel()