Why doesn't "replace" command work as expected in pandas?

Question

I have created the following pandas dataframe:

ds = {"col1":["Mr Stuart (Acting)", "Mr Smith", "John Ross (Acting)"]}
df = pd.DataFrame(data=ds)

Which looks like this:

print(df)
                 col1
0  Mr Stuard (Acting)
1            Mr Smith
2  John Ross (Acting)

I want to replace " (Acting)" (in col1) with nothing.

So I have written this piece of code:

df = df.replace(to_replace=" (Acting)",value="",)

But the " (Acting)" bit is still present in the resulting dataframe:

print(df)
                 col1
0  Mr Stuard (Acting)
1            Mr Smith
2  John Ross (Acting)

Can someone tell me why the replace command is not working? And how can I replace " (Acting)" with nothing?