fix: verify commit msg.

[lsc9]

When I try to make vue core a submodule of my project：

git submodule add https://github.com/vuejs/core.git

do something and git commit:

git commit -am "docs: add comments."

it will throw error：

➜  core git:(heads/v3.4.21) ✗ git commit -am "docs: add comments."
✔ Preparing lint-staged...
✔ Running tasks for staged files...
✔ Applying modifications from tasks...
✔ Cleaning up temporary files...

> @3.4.21 check /Volumes/work_data/Web_data/Web_project/code/Vue3/source/core
> tsc --incremental --noEmit

node:fs:453
    return binding.readFileUtf8(path, stringToFlags(options.flag));
                   ^

Error: ENOTDIR: not a directory, open '/Volumes/work_data/Web_data/Web_project/code/Vue3/source/core/.git/COMMIT_EDITMSG'
    at readFileSync (node:fs:453:20)
    at file:///Volumes/work_data/Web_data/Web_project/code/Vue3/source/core/scripts/verify-commit.js:7:13
    at ModuleJob.run (node:internal/modules/esm/module_job:218:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:329:24)
    at async loadESM (node:internal/process/esm_loader:34:7)
    at async handleMainPromise (node:internal/modules/run_main:113:12) {
  errno: -20,
  code: 'ENOTDIR',
  syscall: 'open',
  path: '/Volumes/work_data/Web_data/Web_project/code/Vue3/source/core/.git/COMMIT_EDITMSG'
}