doc: fix word misspell

[raoqi]

Signed-off-by: raoqi 1020216950@qq.com

Ⅰ. Describe what this PR did

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how you did it

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[CLAassistant]

All committers have signed the CLA.

[pouchrobot]

We found this is your first time to contribute to Pouch, @raoqi
👏 We really appreciate it.
Just remind that you have read the contribution guide: https://github.com/alibaba/pouch/blob/master/CONTRIBUTING.md
If you didn't, you should do that first. If done, welcome again and please enjoy hacking! 🍻

[fuweid]

Hi @raoqi, welcome!

Thank you for your work. LGTM. If the CI passes, I will merge this PR.

Welcome to contribute the pouch!

[codecov-io]

Codecov Report

Merging #1248 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1248   +/-   ##
=======================================
  Coverage   15.31%   15.31%           
=======================================
  Files         172      172           
  Lines       10665    10665           
=======================================
  Hits         1633     1633           
  Misses       8912     8912           
  Partials      120      120

Impacted Files	Coverage Δ
daemon/mgr/spec.go	0% <ø> (ø)	⬆️

[fuweid]

Hold on a sec, @raoqi , the Author is unknown? If it's mistake, please let me know. :)

[allencloud]

the Author is unknown

I think it is OK. We do not strict too much on commit sign off.

[allencloud]

LGTM