[lldb] removed no longer needed CMakeDependentOption

Summary:
In D66791 I've introduced this [[ https://cmake.org/cmake/help/latest/module/CMakeDependentOption.html | `CMakeDependentOption` ]] but in
D71306 @JDevlieghere has changed the way optional dependencies
are handled in LLDB. Today there's no occurence of
`cmake_dependent_option` inside the lldb source tree.

That's why this include can be removed.

Reviewers: JDevlieghere, labath

Reviewed By: labath

Subscribers: labath, mgorny, lldb-commits, JDevlieghere

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D74160