Update Chrono version to 0.4.26,

[panarch]

Update Chrono version and make it not to use pinned version.

resolve #1227

[coveralls]

Pull Request Test Coverage Report for Build 5851326029

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 17 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.03%) to 99.138%

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Files with Coverage Reduction	New Missed Lines	%
core/src/executor/fetch.rs	8	98.17%
core/src/executor/aggregate/mod.rs	9	84.21%

Totals
Change from base Build 5841799820:	-0.03%
Covered Lines:	47506
Relevant Lines:	47919

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💛 - Coveralls