Second minor bugfix to alphabetize-codeowners

Trailing "\n" was picked up on whitespace splitting and created "" as
an "owner" string.

README.md

@@ -179,6 +179,7 @@ following sample config:
 ### Unreleased
 
 <!-- bumpversion-changelog -->
+- Minor whitespace bugfix for `alphabetize-codeowners`
 
 ### 0.6.1
 

src/texthooks/alphabetize_codeowners.py

@@ -48,7 +48,7 @@ def sort_line(line: str) -> str:
  if line == "" or line.strip().startswith("#"):
  return line
  # also normalizes whitespace
- dedented = line.lstrip()
+ dedented = line.lstrip().rstrip()
  elements = WS_PAT.split(dedented)
  if len(elements) < 2:
  return line