Tech debt: Remove moment-timezone transitive dependency

[sadtrick]

Problem

moment-timezone is currently present as a transitive dependency in our project through the following packages:

• caldate
• date-holidays-parser

Both of these packages are marked as extraneous in our dependency tree, meaning they're not listed in our package.json and may have been installed accidentally or leftover from previous dependencies.

Why this matters:

• moment-timezone (and the broader Moment.js ecosystem) is in maintenance mode as of September 2020
• The maintainers recommend using modern alternatives for new projects
• Security updates and new features are no longer being developed
• Bundle size: moment-timezone is relatively large compared to modern alternatives

[commenthol]

Hi @sadtrick, please take a look here commenthol/date-holidays-parser#55