tools: Drop duplicate raise_on_error argument

If kwargs contains raise_on_error then this function generates an error
due to a duplicate argument. Fix this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/patman/command.py b/tools/patman/command.py
index 14edcda..16299f3 100644
--- a/tools/patman/command.py
+++ b/tools/patman/command.py
@@ -108,8 +108,8 @@
     return result
 
 def Output(*cmd, **kwargs):
-    raise_on_error = kwargs.get('raise_on_error', True)
-    return RunPipe([cmd], capture=True, raise_on_error=raise_on_error).stdout
+    kwargs['raise_on_error'] = kwargs.get('raise_on_error', True)
+    return RunPipe([cmd], capture=True, **kwargs).stdout
 
 def OutputOneLine(*cmd, **kwargs):
     raise_on_error = kwargs.pop('raise_on_error', True)