update bin/drspec to use bundle exec

fixes errors such as:

You have already activated activesupport 7.1.5.1, but your Gemfile
requires activesupport 7.0.8.1. Prepending `bundle exec` to your
command may solve this.

this can occur when switching between branches that uses different Rails
versions. e.g. switching between the branch used for the 7.1 upgrade and
a branch that was still on 7.0.

Author: mikej

bin/drspec

@@ -2,4 +2,4 @@
 
 set -e
 
-docker compose exec web rspec $@
+docker compose exec web bundle exec rspec $@