cmTarget: Remove unused classes cmTargetSet and cmTargetManifest

Source/cmTarget.cxx

@@ -6,7 +6,6 @@
 #include <algorithm>
 #include <assert.h>
 #include <iterator>
-#include <map>
 #include <set>
 #include <sstream>
 #include <string.h>

Source/cmTarget.h

@@ -6,7 +6,6 @@
 #include "cmConfigure.h" // IWYU pragma: keep
 
 #include <iosfwd>
-#include <map>
 #include <set>
 #include <string>
 #include <unordered_map>
@@ -344,11 +343,4 @@ private:
 
 typedef std::unordered_map<std::string, cmTarget> cmTargets;
 
-class cmTargetSet : public std::set<std::string>
-{
-};
-class cmTargetManifest : public std::map<std::string, cmTargetSet>
-{
-};
-
 #endif