Convert `rem` to base font size #9848

Job	Run time
Clients-Cypress (20.x, admin-ui)	15m 24s
Clients-Cypress-Component (20.x, admin-ui)	1m 39s
Clients-Cypress (20.x, privacy-center)	8m 11s
Clients-Unit (20.x, admin-ui)	3m 33s
Clients-Unit (20.x, privacy-center)	3m 12s
Clients-Unit (20.x, fides-js)	3m 15s
	35m 14s

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