tools: remove unused using declarations

PR-URL: #28422
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

tools/snapshot/snapshot_builder.cc

@@ -10,8 +10,6 @@ namespace node {
 using v8::Context;
 using v8::HandleScope;
 using v8::Isolate;
-using v8::Local;
-using v8::Locker;
 using v8::SnapshotCreator;
 using v8::StartupData;