OPT: Bump pg from 1.5.8 to 1.5.9 #530

Job	Run time
Build Image / Cypress	1m 2s
Build Image / Preview	2m 35s
Build Image / Development	2m 38s
Build Image / Production	2m 43s
Build Image / Test	2m 42s
Lint / ESLint	39s
Lint / ESLint - Tests	44s
Preview / Deploy	3s
Lint / Reek	20s
Lint / Brakeman	20s
Lint / Bundler Audit	20s
Tests / End-to-end - Admin (chrome)	4m 42s
Tests / End-to-end - Admin (firefox)	5m 3s
Lint / Rubocop	26s
Tests / End-to-end - Frontend (chrome)	1m 43s
Lint / SCSSLint	24s
Tests / End-to-end - Frontend (firefox)	1m 39s
Tests / Backend	50s
	28m 53s

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