[BUG]: Some mocks with time data don't render proper in non-UTC time zones

[camdecoster]

Description

The following mocks render properly in CI (which uses UTC) but not locally:

• test/image/mocks/axes_breaks.json
• test/image/mocks/domain_ref_axis_types.json

Screenshots/Video

axes_breaks

CI	Local

Steps to reproduce

• Run plotly devtools
• Open up one of the mocks listed above
• Note that the resulting image is different from the baseline image (built from CI runs)

Notes

• The issue has to do with how time zones are handled when no time info is included in the data point