ensure-dirs: Fix program name on usage screen

No string replacements are used, so doubling of the percent sign is not
necessary.

Before: Usage: %ensure-dirs [--full-run]
After: Usage: ensure-dirs [--full-run]

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

lib/tools/ensure_dirs.py

@@ -224,7 +224,7 @@ def ParseOptions():
   """
   program = os.path.basename(sys.argv[0])
 
-  parser = optparse.OptionParser(usage="%%prog [--full-run]",
+  parser = optparse.OptionParser(usage="%prog [--full-run]",
                                  prog=program)
   parser.add_option(cli.DEBUG_OPT)
   parser.add_option(cli.VERBOSE_OPT)