Fix update-tests-metadata CI job

The upgrade to Ruby v2.7.2 meant that only bundler v2 was installed by
default. rspec_profiling v0.0.5 required bundler v1, but v0.0.6 relaxed
the dependency to allow for bundler 2 (see
https://github.com/foraker/rspec_profiling/commit/6ad1ec4e37).