chore: fix coverage computation to ignore types (#101)

Author: JoshuaKGoldberg

package.json

@@ -10,7 +10,7 @@
 		"@semantic-release/release-notes-generator": "^10.0.3",
 		"@typescript-eslint/eslint-plugin": "^5.38.1",
 		"@typescript-eslint/parser": "^5.38.1",
-		"@vitest/coverage-c8": "^0.25.4",
+		"@vitest/coverage-istanbul": "^0.25.8",
 		"chalk": "^5.1.2",
 		"cspell": "^6.12.0",
 		"eslint": "^8.24.0",