libprocessgroup: Don't delegate to default constructor

Manually calling a defaulted default constructor from a another
constructor is superfluous, and can increase code size if the default
constructor is not otherwise used. There's nothing to delegate, so
remove the call.

Bug: 346584259
Test: m
Change-Id: Ia16aa041fdee7434587cf90645d7f95cba4e0d10
1 file changed