deprecation warning Bundler.rubygems.all_specs

- fix deprecation warning while starting `rails server`
  - `[DEPRECATED] Bundler.rubygems.all_specs has been removed in favor of Bundler.rubygems.installed_specs`
- reproducible with ruby v3.3.3 (and new minimum required bundler, rubygems versions)

lib/scout_apm/utils/installed_gems.rb

@@ -12,7 +12,7 @@ def logger
       end
 
       def run
-        Bundler.rubygems.all_specs.map {|spec| [spec.name, spec.version.to_s] }
+        Bundler.rubygems.installed_specs.map {|spec| [spec.name, spec.version.to_s] }
       rescue => e
         logger.warn("Couldn't fetch Gem information: #{e.message}")
         []