fix: v-scroll directive event listener leak

[rocka]

There's a heavy event listener leak when using v-scroll directive.

The performance profile was captured in https://muse-ui.org/#/zh-CN/directives . When the page scrolls, there's just tons of event listeners been attached, but none of them got removed.

https://github.com/museui/muse-ui/blob/master/src/internal/directives/scroll.js#L38

I think the update function in this directive was totally unnecessary, according to Vue Custom Directive Guide.

To demonstrate this, there's a fiddle: https://jsfiddle.net/zgrxt69h/ . update was removed, and it still works fine.

[codecov-io]

Codecov Report

Merging #1365 into master will decrease coverage by 0.19%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #1365     +/-   ##
=========================================
- Coverage   30.18%   29.98%   -0.2%     
=========================================
  Files         220      220             
  Lines        3578     3578             
  Branches      749      749             
=========================================
- Hits         1080     1073      -7     
- Misses       1880     1885      +5     
- Partials      618      620      +2

Impacted Files	Coverage Δ
src/internal/directives/scroll.js	81.25% <ø> (ø)	⬆️
src/utils/dom.js	0% <0%> (-13.21%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 74f78df...874031d. Read the comment docs.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 29.98%. Comparing base (74f78df) to head (874031d).
⚠️ Report is 1 commits behind head on master.
❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1365      +/-   ##
==========================================
- Coverage   30.18%   29.98%   -0.20%     
==========================================
  Files         220      220              
  Lines        3578     3578              
  Branches      749      749              
==========================================
- Hits         1080     1073       -7     
- Misses       1880     1885       +5     
- Partials      618      620       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.