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

@@ -14,7 +14,7 @@ GEM
     addressable (2.8.6)
       public_suffix (>= 2.0.2, < 6.0)
     base64 (0.2.0)
-    bigdecimal (3.1.5)
+    bigdecimal (3.1.6)
     coffee-script (2.4.1)
       coffee-script-source
       execjs