Revert "Disable regabi due to on-going stability issues (#4245)" (#4365)

This reverts commit 2a3e589.

Reverts REGABI disabling change since the issue was resolved in Go 1.17.6, and no longer impacts the SDK's code generation.

Makefile

@@ -38,7 +38,7 @@ gen-codegen-test:
 
 gen-services:
 	@echo "Generating SDK clients"
-	env GOEXPERIMENT=noregabi go generate ./service
+	go generate ./service
 
 gen-protocol-test:
 	@echo "Generating SDK protocol tests"