fix: additional newline added to docstring when the previous line length is less than the line length limit minus 1

[veryslowcode]

Description

 This resolves the issue mentioned in issue #4180, where a newline will
 be added to a docstring comment (that is approaching the line limit),
 even if the docstring contains a newline before the closing quotes.

Checklist - did you ...

• [✓] Add an entry in CHANGES.md if necessary?
• [✓] Add / update tests if necessary?
• [✓] Add new / update outdated documentation?

[github-actions]

diff-shades results comparing this PR (8a42112) to main (632f44b). The full diff is available in the logs under the "Generate HTML diff report" step.

╭─────────────────────── Summary ────────────────────────╮
│ 5 projects & 9 files changed / 9 changes [+0/-9]       │
│                                                        │
│ ... out of 2 530 293 lines, 12 163 files & 22 projects │
╰────────────────────────────────────────────────────────╯

Differences found.

What is this? | Workflow run | diff-shades documentation

[veryslowcode]

I see that diff-shades detected changes, but they appear to be the intended changes based on the original issue. If there is anything remaining that needs to be done/changed, please let me know and I am happy to do so.

[JelleZijlstra]

Thanks, this is close to being ready.