docs(CHANGES): Fix typo

Author: tony

CHANGES

@@ -31,7 +31,7 @@ $ pipx install --suffix=@next 'tmuxp' --pip-args '\--pre' --force
   - Clean up CodeQL
 
 - Bump poetry 1.1.x -> 1.2.x
-- Bump libtmux 0.15.1 -> 0.15.6
+- Bump libtmux 0.15.1 -> 0.15.7
   - 0.15.7 (move `.coveragerc` -> `pyproject.toml`)
   - 0.15.6 (#823, pytest fixes, packaging improvements)
   - 0.15.3 (#821, pytest plugin improvements, root-level