ci: Update run_loadtest_from_github_actions (#3488)

## What ❔

make script work after Cargo.toml was moved

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bin/run_loadtest_from_github_actions

@@ -19,4 +19,4 @@ export CONTRACT_EXECUTION_PARAMS_RECURSIVE_CALLS=${execution_params[5]}
 export CONTRACT_EXECUTION_PARAMS_DEPLOYS=${execution_params[6]}
 
 # Run the test
-cargo run --bin loadnext
+cd core && cargo run --bin loadnext