Fix Julia 1.12 explicit qualification required warnings

[omus]

❯ julia --project -e '@show VERSION; using TimeZones'
VERSION = v"1.12.0-DEV.2047"
Info Given TimeZones was explicitly requested, output will be shown live
WARNING: Constructor for type "DateTime" was extended in `TimeZones` without explicit qualification or import.
  NOTE: Assumed "DateTime" refers to `Dates.DateTime`. This behavior is deprecated and may differ in future versions.`
  NOTE: This behavior may have differed in Julia versions prior to 1.12.
  Hint: If you intended to create a new generic function of the same name, use `function DateTime end`.
  Hint: To silence the warning, qualify `DateTime` as `Dates.DateTime` or explicitly `import Dates: DateTime`
WARNING: Constructor for type "Date" was extended in `TimeZones` without explicit qualification or import.
  NOTE: Assumed "Date" refers to `Dates.Date`. This behavior is deprecated and may differ in future versions.`
  NOTE: This behavior may have differed in Julia versions prior to 1.12.
  Hint: If you intended to create a new generic function of the same name, use `function Date end`.
  Hint: To silence the warning, qualify `Date` as `Dates.Date` or explicitly `import Dates: Date`
WARNING: Constructor for type "Time" was extended in `TimeZones` without explicit qualification or import.
  NOTE: Assumed "Time" refers to `Dates.Time`. This behavior is deprecated and may differ in future versions.`
  NOTE: This behavior may have differed in Julia versions prior to 1.12.
  Hint: If you intended to create a new generic function of the same name, use `function Time end`.
  Hint: To silence the warning, qualify `Time` as `Dates.Time` or explicitly `import Dates: Time`
Precompiling TimeZones finished.
  1 dependency successfully precompiled in 4 seconds. 22 already precompiled.
  1 dependency had output during precompilation:
┌ TimeZones
│  [Output was shown above]
└