[lldb][NFC] Remove strange bool parameter from Searcher::SearchCallback
The SearchCallback has a bool parameter that we always set to false, we never use in any callback implementation and that also changes its name
from one file to the other (either containing and complete). It was added in the original LLDB check in, so there isn't any history what
this was supposed to be, so let's just remove it.
Reviewers: jingham, JDevlieghere, labath
Reviewed By: jingham, labath
Differential Revision: https://reviews.llvm.org/D68696