Remove use of tree.h

All code using tree.h where commented.
As tree.h where install by kiwix-lib and we removed it there, let's remove
its use here.

src/reader/kiwix-read.cpp

@@ -18,7 +18,6 @@
  */
 
 #include <getopt.h>
-#include <kiwix/common/tree.h>
 #include <kiwix/reader.h>
 #include <unistd.h>
 #include <map>
@@ -30,12 +29,6 @@ void usage()
   exit(1);
 }
 
-void updateSuggestionTree(tree<pair<string, unsigned>>& suggestionTree,
-                          string suggestion)
-{
-  return;
-}
-
 int main(int argc, char** argv)
 {
   /* Init the variables */
@@ -108,9 +101,6 @@ int main(int argc, char** argv)
     }
     */
 
-    //    tree< pair<string, unsigned> > tree;
-    // updateSuggestionTree(tree, string(suggestion));
-
     delete reader;
   } else {
     cerr << "Unable instanciate the Kiwix reader." << endl;