CMake: Remove CMakeProject::buildTargetTitles

The only user can also get this information from the relevant
CMakeBuildConfiguration.

Change-Id: I80e176ef0a8bc427f6adbf75b20e29f38d7b949f
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cmakeprojectmanager/cmakeproject.h

@@ -63,8 +63,6 @@ public:
     explicit CMakeProject(const Utils::FilePath &filename);
     ~CMakeProject() final;
 
-    QStringList buildTargetTitles() const;
-
     ProjectExplorer::Tasks projectIssues(const ProjectExplorer::Kit *k) const final;
 
     void runCMake();