fix(datetime): keyboard can select hour 00

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue URL: resolves #26409

The regular expression for text entry stripped a string of all leading zeros. As a result, the 24 hour time entry for midnight ('00') became the empty string ('') which never matched the input value.

What is the new behavior?

• Updated the regular expression to allows at least one 0 to pass through unfiltered if the entire string contains zeros.

Does this introduce a breaking change?

• Yes
• No

Other information