Update datetime.rst

Fixed "the the" typo.
Update datetime.rst
minor #4185 [Components][Form] Fixed typo in datetime type reference (althaus)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4185).

Discussion
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[Components][Form] Fixed typo in datetime type reference

Fixed "the the" typo.

Commits
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7c42e4b Update datetime.rst
d556309 Update datetime.rst