Bump FluentAssertions from 8.2.0 to 8.9.0 #643

Job	Run time
Lint & Approval Tests	47s
Integrations Tests (3.13, ubuntu-latest)	2m 9s
Integrations Tests (3.12, ubuntu-latest)	2m 5s
Unit Tests (ubuntu-latest, net8.0)	35s
Integrations Tests (4.0, ubuntu-latest)	1m 58s
Unit Tests (windows-latest, net48)	1m 25s
Publish to NuGet	0s
	8m 59s

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