Perhaps you can use sed:
sed 's/\x20\x28//g' <file_in.txt >file_out.txt
To overwrite the original file:
sed -i 's/\x20\x28//g' file.txt
Edit : (see chepner comment). You have to make sure that you have the correct bytes, depending on the encoding, and then use sed to remove them. You can use for example. od -t x1 to view the hex dump and determine the encoding.
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