Remove unnecessary /* eslint no-var: error */ lines in the test/unit/ folder (PR 12528 follow-up)

These lines are no longer needed, since the ESLint `no-var` rule has been enabled in the entire folder.

test/unit/display_utils_spec.js

@@ -12,7 +12,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint no-var: error */
 
 import {
   DOMCanvasFactory,

test/unit/fetch_stream_spec.js

@@ -12,7 +12,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint no-var: error */
 
 import { AbortException } from "../../src/shared/util.js";
 import { PDFFetchStream } from "../../src/display/fetch_stream.js";

test/unit/parser_spec.js

@@ -12,7 +12,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint no-var: error */
 
 import { Lexer, Linearization, Parser } from "../../src/core/parser.js";
 import { FormatError } from "../../src/shared/util.js";