Fix incorrect gl- utility class

What does this MR do and why?

Fixes the flex direction class

• Replace gl-flex-column with gl-flex-direction-column

Screenshots or screen recordings

No visual changes, by default the column direction is applied, so this worked implicitly although the class used doesnt exist in https://unpkg.com/browse/@gitlab/ui@42.22.0/src/scss/utilities.scss

How to set up and validate locally

1. Apply this patch

diff --git a/ee/spec/features/billings/billing_plans_spec.rb b/ee/spec/features/billings/billing_plans_spec.rb
index 7b2851f3159..dfa3f759cf7 100644
--- a/ee/spec/features/billings/billing_plans_spec.rb
+++ b/ee/spec/features/billings/billing_plans_spec.rb
@@ -118,6 +118,7 @@ def external_upgrade_url(namespace, plan)
 
     it 'displays subscription table' do
       expect(page).to have_selector('.js-subscription-table')
+      binding.pry
     end
   end
 

2. Run the billing plans spec in a headless browser and play around with the responsive stylinh

CHROME_HEADLESS=0 bin/spring rspec ./ee/spec/features/billings/billing_plans_spec.rb:155

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.