Pin version of flask-appbuilder since its 2.3.3 causes issue

[XD-DENG]

the issue is reported in #8613.

I confirmed it, and confirmed downgrading flask-appbuilder to 2.3.2 can fix (its 2.3.3 was released yesterday).

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[kaxil]

I think this is solved by #8602

[XD-DENG]

@kaxil ha, cool, sorry I didn't check the earlier PR. Nice it's already fixed.

[kaxil]

:)