Update tbump requirement from ~=6.8.0 to ~=6.9.0 (#1569)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_test.txt

@@ -6,6 +6,6 @@ coverage~=6.3.3
 pre-commit~=2.19
 pytest-cov~=3.0
 contributors-txt>=0.7.3
-tbump~=6.8.0
+tbump~=6.9.0
 types-typed-ast; implementation_name=="cpython" and python_version<"3.8"
 types-pkg_resources==0.1.3