fix(migrate): drop redundant casts flagged by oxlint-tsgolint 0.24.0

The merge to main bumped oxlint-tsgolint to 0.24.0, whose
no-unnecessary-type-assertion rule flags three more redundant readJsonFile
casts. #2000 removed the ones in main's monolith; these live in split modules
(vite-plus-bootstrap.ts) and a test, so they were missed by the merge. Remove
them so vp check passes.

Claude-Session: https://claude.ai/code/session_01DQhS6o1fyQd1yjiee6W8jR

Author: fengmk2

packages/cli/src/migration/__tests__/migrator.spec.ts

@@ -1126,10 +1126,7 @@ describe('collectInstalledPackageNames', () => {
     });
     const available = collectInstalledPackageNames(tmpDir);
     const config = { jsPlugins: ['eslint-plugin-only-peer'] };
-    sanitizeMigratedOxlintConfig(
-      config as Parameters<typeof sanitizeMigratedOxlintConfig>[0],
-      available,
-    );
+    sanitizeMigratedOxlintConfig(config, available);
     expect(config.jsPlugins).toEqual([]);
   });
 });

packages/cli/src/migration/migrator/vite-plus-bootstrap.ts

@@ -536,7 +536,7 @@ function someBootstrapProjectPackageJson(
     if (!fs.existsSync(packageJsonPath)) {
       return false;
     }
-    return predicate(readJsonFile(packageJsonPath) as BootstrapPackageJson);
+    return predicate(readJsonFile(packageJsonPath));
   });
 }
 
@@ -1201,7 +1201,7 @@ function readInstalledRawViteVersion(projectPath: string): string | undefined {
   }
   let pkgJson: RawVitePackageJson;
   try {
-    pkgJson = readJsonFile(vitePackageJsonPath) as RawVitePackageJson;
+    pkgJson = readJsonFile(vitePackageJsonPath);
   } catch {
     return undefined;
   }