test: Install older version of bson for JRuby (#1567)

* test: Install older version of bson for JRuby

At this time, bson 5.1.0 is not compatible with JRuby. However, older
versions are compatible. Install the latest version below the
incompatible one.

* chore: Rubocop

Author: kaylareopelle

instrumentation/mongo/Appraisals

@@ -6,4 +6,7 @@
 
 appraise 'mongo-2' do
   gem 'mongo', '~> 2.13'
+
+  # TODO: bson 5.1.0 isn't compatible with JRuby as of 2025/06/17
+  gem 'bson', '< 5.1.0' if defined?(JRUBY_VERSION)
 end