wasm_test: Update test wasm file: use latest graph-ts, update mappings

Author: fordN

runtime/wasm/wasm_test/example_event_handler.md

@@ -1,2 +1,2 @@
 The source for `example_event_handler.wasm` is the WASM output of
-https://github.com/graphprotocol/graph-cli/tree/master/examples/example-event-handler.
+https://github.com/graphprotocol/graph-cli/tree/ford/setup-test-wasm/examples/example-subgraph