Adds Int Support competencies

Why is this change being made?

Support needs to add competencies to the new career matrices for Engineering. This MR adds the intermediate level ones.

Closes gitlab-com/support/support-team-meta#2423 (closed)

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sites/handbook/source/handbook/engineering/career-development/matrix/engineering/support/intermediate/_support_intermediate_leadership_competency.erb

-* Intermediate Leadership Competency 1
-* Intermediate Leadership Competency 2
-* Intermediate Leadership Competency 3
+* Demonstrates a personal growth mindset by initiating pairings, completing bootcamps and building product and troubleshooting knowledge.
+* Understands support KPIs and optimizes personal workflow towards team achievement.