Add missing ' in documentation

[LeeTeng2001]

Motivation

Fix typo in documentation

Modification

I've added a closing ' to the documentation

Who can help? @ them here!

Checklist

Before PR:

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

[LeoXing1996]

Hey @LeeTeng2001, thanks for your contribution. This modification looks good to me.

BTW, MMGeneration had merged into MMEditing dev-1.x, and no more new features will be supported in MMGeneration. So, we would like to encourage you to use MMEditing.

[OpenMMLab-Assistant001]

Hi @LeeTeng2001 ！First of all, we want to express our gratitude for your significant PR in the MMGeneration . 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.

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Thank you again for your contribution！❤