hiddenapi: Fix map insertion bug

`hiddenapi` would use std::map::insert to overwrite an entry, which
is wrong and will not overwrite the entry. This caused all entries
to be classified as private. Fix the bug.

Bug: 79409988
Test: m appcompat, check hiddenapi-public-list.txt not empty
Change-Id: Ie1c1fad2dfff9ff0332b5196d605d512d6dedc15
diff --git a/tools/hiddenapi/hiddenapi.cc b/tools/hiddenapi/hiddenapi.cc
index c252a9b..0381381 100644
--- a/tools/hiddenapi/hiddenapi.cc
+++ b/tools/hiddenapi/hiddenapi.cc
@@ -655,7 +655,7 @@
                 if (it->second) {
                   return false;  // has been marked before
                 } else {
-                  boot_members.insert(it, std::make_pair(entry, true));
+                  it->second = true;
                   return true;  // marked for the first time
                 }
               });