Update MTA_PLUGIN_VERSION to 2.6.3 (#40)

Author: fwilhe

Dockerfile

@@ -20,7 +20,7 @@ RUN addgroup -gid 1000 piper && \
 USER piper
 WORKDIR ${USER_HOME}
 
-ARG MTA_PLUGIN_VERSION=2.5.1
+ARG MTA_PLUGIN_VERSION=2.6.3
 ARG MTA_PLUGIN_URL=https://github.com/cloudfoundry-incubator/multiapps-cli-plugin/releases/download/v${MTA_PLUGIN_VERSION}/mta_plugin_linux_amd64
 ARG CSPUSH_PLUGIN_VERSION=1.3.2
 ARG CSPUSH_PLUGIN_URL=https://github.com/dawu415/CF-CLI-Create-Service-Push-Plugin/releases/download/${CSPUSH_PLUGIN_VERSION}/CreateServicePushPlugin.linux64