Add welcomebot and aws-SNS to prepackaged plugins (#11048)

Makefile

@@ -76,6 +76,8 @@ TE_PACKAGES=$(shell go list ./...|grep -v plugin_tests)
 # Plugins Packages
 PLUGIN_PACKAGES=mattermost-plugin-zoom-v1.0.6
 PLUGIN_PACKAGES += mattermost-plugin-autolink-v1.0.0
+PLUGIN_PACKAGES += mattermost-plugin-welcomebot-v1.0.0
+PLUGIN_PACKAGES += mattermost-plugin-aws-SNS-v1.0.0
 
 # Prepares the enterprise build if exists. The IGNORE stuff is a hack to get the Makefile to execute the commands outside a target
 ifeq ($(BUILD_ENTERPRISE_READY),true)