Update core version as a follow up pr to #670. (#672)

Author: fnando

Makefile

@@ -25,7 +25,7 @@ build-latest:
 	$(MAKE) build TAG=latest \
 		PROTOCOL_VERSION_DEFAULT=22 \
 		XDR_REF=v22.0.0 \
-		CORE_REF=v22.0.0 \
+		CORE_REF=v22.2.0 \
 		HORIZON_REF=horizon-v22.0.2 \
 		STELLAR_RPC_REF=v22.1.2 \
 		FRIENDBOT_REF=horizon-v22.0.2
@@ -34,7 +34,7 @@ build-testing:
 	$(MAKE) build TAG=testing \
 	    PROTOCOL_VERSION_DEFAULT=22 \
 		XDR_REF=v22.0.0 \
-		CORE_REF=v22.0.0 \
+		CORE_REF=v22.2.0 \
 		HORIZON_REF=horizon-v22.0.2 \
 		STELLAR_RPC_REF=v22.1.2 \
 		FRIENDBOT_REF=horizon-v22.0.2
@@ -43,7 +43,7 @@ build-future:
 	$(MAKE) build TAG=future \
 		PROTOCOL_VERSION_DEFAULT=22 \
 		XDR_REF=v22.0.0 \
-		CORE_REF=v22.0.0 \
+		CORE_REF=v22.2.0 \
 		HORIZON_REF=horizon-v22.0.2 \
 		STELLAR_RPC_REF=v22.1.2 \
 		FRIENDBOT_REF=horizon-v22.0.2