[Docs] fix docstring

[dienachtderwelt]

Thanks for your contribution and we appreciate it a lot. The following instructions would make your pull request more healthy and more easily get feedback. If you do not understand some items, don't worry, just make the pull request and seek help from maintainers.

Motivation

First PR. Just a mini doc fix as a try LOL.

Modification

Change argname in docstring to match the actual arguments.

Checklist

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• New functionalities are covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with some of those projects.
• CLA has been signed and all committers have signed the CLA in this PR.

[CLAassistant]

All committers have signed the CLA.

[liuwenran]

It is exactly a typo. Thanks for your contribution.

[codecov]

Codecov Report

Base: 87.90% // Head: 87.90% // No change to project coverage 👍

Coverage data is based on head (d3bfc3e) compared to base (e7c0539).
Patch has no changes to coverable lines.

❗ Current head d3bfc3e differs from pull request most recent head 0bc3ab0. Consider uploading reports for the commit 0bc3ab0 to get more accurate results

Additional details and impacted files

@@           Coverage Diff            @@
##           dev-1.x    #1578   +/-   ##
========================================
  Coverage    87.90%   87.90%           
========================================
  Files          399      399           
  Lines        26015    26015           
  Branches      4044     4044           
========================================
  Hits         22868    22868           
  Misses        2240     2240           
  Partials       907      907           

Flag	Coverage Δ
unittests	87.90% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmedit/datasets/transforms/aug_pixel.py	96.36% <ø> (ø)

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[liuwenran]

@dienachtderwelt BTW, if you are interested in image editing algorithms, we are looking forward to more contribution. Lets make this repo better together. 😃

[jason102811]

Dear dienachtderwelt,
First of all, we want to express our gratitude for your significant PR in the MMEditing . Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
As a valued contributor, we would also like to invite you to join our Special Interest Group (SIG) private channel, where you can share your experiences, ideas, and build connections with like-minded peers.
Join us ：https://discord.gg/raweFPmdzG
To join the SIG channel, simply message moderator— OpenMMLab on Discord or briefly share your open-source contributions in the #introductions channel and we will assist you. We look forward to seeing you there!
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Best regards！ @dienachtderwelt