gh-41252: Fix formatting of warning message in meson.build
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes #12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes #12345". -->

Otherwise CI fails on every PR.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - #12345: short description why this is a dependency -->
<!-- - #34567: ... -->
    
URL: #41252
Reported by: Tobias Diez
Reviewer(s): Chenxin Zhong

Author: Release Manager

src/doc/meson.build

@@ -2,7 +2,9 @@ if not get_option('build-docs')
   subdir_done()
 endif
 
-warning('Documentation building enabled, generating targets may be slow. To disable this, pass -Dbuild-docs=false.')
+warning(
+  'Documentation building enabled, generating targets may be slow. To disable this, pass -Dbuild-docs=false.',
+)
 
 sphinx_check = py_module.find_installation(required: false, modules: ['sphinx'])
 if not sphinx_check.found()