chore: fix docker build (#35)

Makefile

@@ -42,7 +42,7 @@ $(BUILDDIR)/:
 	mkdir -p $(BUILDDIR)/
 
 build-docker:
-	$(DOCKER) build --secret id=sshKey,src=${BBN_PRIV_DEPLOY_KEY} --tag babylonlabs-io/btc-staker -f Dockerfile \
+	$(DOCKER) build --tag babylonlabs-io/btc-staker -f Dockerfile \
 		$(shell git rev-parse --show-toplevel)
 
 .PHONY: build build-docker