chore: use fluvio `0.11.8` #270

Job	Run time
Integration Testing on ubuntu-latest for http-sink connector.	6m 47s
Rust Check - test	3m 45s
Rust Check - check	2m 43s
Rust Check - fmt	28s
Rust Check - clippy	2m 40s
Done	1s
	16m 24s

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