Bump bigdecimal from 3.1.5 to 3.1.6

Bumps [bigdecimal](https://github.com/ruby/bigdecimal) from 3.1.5 to 3.1.6.
- [Release notes](https://github.com/ruby/bigdecimal/releases)
- [Changelog](https://github.com/ruby/bigdecimal/blob/master/CHANGES.md)
- [Commits](ruby/bigdecimal@v3.1.5...v3.1.6)

---
updated-dependencies:
- dependency-name: bigdecimal
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    bigdecimal (3.1.5)
+    bigdecimal (3.1.6)
     jsonlint (0.4.0)
       oj (~> 3)
       optimist (~> 3)