chore(react-router): Internal environment variables clean up #12939

Job	Run time
check-permissions	2s
Formatting, linting & changeset checks	2m 36s
Unit Tests (18)	56s
Integration Tests (generic, chrome)	4m 20s
Unit Tests (22)	2m 5s
Integration Tests (express, chrome)	2m 6s
Integration Tests (quickstart, chrome)	3m 11s
Integration Tests (ap-flows, chrome)	2m 58s
Integration Tests (elements, chrome)	2m 41s
Integration Tests (sessions, chrome)	3m 58s
Integration Tests (astro, chrome)	3m 21s
Integration Tests (expo-web, chrome)	2m 41s
Integration Tests (tanstack-start, chrome)	2m 8s
Integration Tests (tanstack-router, chrome)	2m 2s
Integration Tests (vue, chrome)	1m 58s
Integration Tests (nuxt, chrome)	2m 53s
Integration Tests (react-router, chrome)	2m 4s
Integration Tests (nextjs, chrome, 13)	5m 33s
Integration Tests (nextjs, chrome, 14)	6m 13s
Integration Tests (nextjs, chrome, 15)	6m 18s
	1h 0m 4s

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