STYLE: Remove empty line from doc file (pre-commit "fix end of files")

[N-Dekker]

Locally ran pixi at the root of ITK source tree, as follows:

./.git/hooks/pixi/bin/pixi.exe run pre-commit-run

Output:

Pixi task (pre-commit-run in pre-commit): pre-commit run --all: (Run pre-commit hooks on all repository files)
check for added large files..............................................Passed
[...]
fix end of files.........................................................Failed
- hook id: end-of-file-fixer
- exit code: 1
- files were modified by this hook

[thewtex]

@N-Dekker thanks!