Update pstore to 0.2.1 [Backport #21880]

Fix ultra_safe mode of pstore bundled with Ruby 4.0.

Author: k0kubun

gems/bundled_gems

@@ -36,7 +36,7 @@ syslog              0.3.0   https://github.com/ruby/syslog
 csv                 3.3.5   https://github.com/ruby/csv
 repl_type_completor 0.1.12  https://github.com/ruby/repl_type_completor
 ostruct             0.6.3   https://github.com/ruby/ostruct
-pstore              0.2.0   https://github.com/ruby/pstore
+pstore              0.2.1   https://github.com/ruby/pstore
 benchmark           0.5.0   https://github.com/ruby/benchmark
 logger              1.7.0   https://github.com/ruby/logger
 rdoc                7.0.3   https://github.com/ruby/rdoc