Fix: remove leftover block_on from `graphman chain change-shard` #10989

Job	Run time
Build in release mode	1m 33s
Check rustfmt style	17s
Run unit tests	2m 42s
Run integration tests	4m 0s
Subgraph Runner integration tests	2m 28s
Clippy linting	1m 57s
	12m 57s

Provide feedback