Update bundled bigdecimal to 3.3.1

Author: tompng

gems/bundled_gems

@@ -25,7 +25,7 @@ racc                1.8.1   https://github.com/ruby/racc
 mutex_m             0.3.0   https://github.com/ruby/mutex_m
 getoptlong          0.2.1   https://github.com/ruby/getoptlong
 base64              0.3.0   https://github.com/ruby/base64
-bigdecimal          3.2.2   https://github.com/ruby/bigdecimal
+bigdecimal          3.3.1   https://github.com/ruby/bigdecimal
 observer            0.1.2   https://github.com/ruby/observer
 abbrev              0.1.2   https://github.com/ruby/abbrev
 resolv-replace      0.1.1   https://github.com/ruby/resolv-replace