style: remove stray import

As reported by `yarn lint`:

    packages/lexer/src/RegExp/RegExpParser.ts:1:1 - error TS6192: All imports in import declaration are unused.

    1 import {describe, expect, it} from '@jest/globals';
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

packages/lexer/src/RegExp/RegExpParser.ts

@@ -1,4 +1,3 @@
-import {describe, expect, it} from '@jest/globals';
 import {StringScanner, invariant} from '@masochist/common';
 
 import normalizeCharacterClass from './normalizeCharacterClass';