import re
pattern = r"\s*\)(?:\s{2,})?([^\W)])?"
input_text = "((PL_ADVB)dentro ). ((PL_ADVB)ñu)((PL_ADVB) 9u)"
res = re.sub(pattern, lambda m: ") " + m.group(1) if m.group(1) else ")", input_text)
print(res)
aW1wb3J0IHJlCgpwYXR0ZXJuID0gciJccypcKSg/OlxzezIsfSk/KFteXFcpXSk/IgppbnB1dF90ZXh0ID0gIigoUExfQURWQilkZW50cm8gKS4gKChQTF9BRFZCKcOxdSkoKFBMX0FEVkIpICAgIDl1KSIKcmVzID0gcmUuc3ViKHBhdHRlcm4sIGxhbWJkYSBtOiAiKSAiICsgbS5ncm91cCgxKSBpZiBtLmdyb3VwKDEpIGVsc2UgIikiLCBpbnB1dF90ZXh0KQpwcmludChyZXMp