Fix tbump

[forsyth2]

Summary

Objectives:

• Resolve tbump error noted in Bump to 1.5.0rc1 #389.

Select one: This pull request is...

• a bug fix: increment the patch version
• a small improvement: increment the minor version
• a new feature: increment the minor version
• an incompatible (non-backwards compatible) API change: increment the major version

Small Change

• To merge, I will use "Squash and merge". That is, this change should be a single commit.
• Logic: I have visually inspected the entire pull request myself.
• Pre-commit checks: All the pre-commits checks have passed.

[forsyth2]

With this change tbump 1.5.0rc2 --no-tag produced a commit with the expected changes. Therefore, this should be good to merge. @tomvothecoder Let me know if I should change anything else, thanks.

[tomvothecoder]

LGTM