test(eslint-plugin): update filename from relative to absolute path

this should be fixed when #1424 gets merged

packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts

@@ -135,7 +135,7 @@ function Test(props: {
   return <div key={props.id!} />;
 };
       `,
-      filename: 'react.tsx',
+      filename: path.join(rootDir, 'react.tsx'),
     },
   ],
 
@@ -373,7 +373,7 @@ function Test(props: {
           line: 7,
         },
       ],
-      filename: 'react.tsx',
+      filename: path.join(rootDir, 'react.tsx'),
     },
   ],
 });