test: use `ecmaVersion: "latest"` in tests #3778

Job	Run time
Test for Svelte v4 on Node.js: 20 OS: ubuntu-latest	46s
Test for Svelte v4 on Node.js: 18 OS: ubuntu-latest	50s
Test for Svelte v4 on Node.js: 22 OS: ubuntu-latest	46s
update-resources	41s
Test for Svelte v3 (ubuntu-latest, 18)	48s
build	1m 21s
lint	3m 28s
Test for ESLint 8 on Node.js: 20.x OS: ubuntu-latest	1m 28s
Test for ESLint 8 on Node.js: 18.x OS: ubuntu-latest	1m 39s
Test for ESLint 8 on Node.js: latest OS: ubuntu-latest	1m 22s
Test for ESLint 8 on Node.js: 22.x OS: ubuntu-latest	1m 20s
Test for ESLint 9 on Node.js: 18.x OS: ubuntu-latest	1m 31s
Test for ESLint 9 on Node.js: 22.x OS: ubuntu-latest	1m 24s
Test for ESLint 9 on Node.js: latest OS: ubuntu-latest	1m 25s
Test for ESLint 9 on Node.js: 20.x OS: ubuntu-latest	1m 25s
	20m 14s

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