Groovy 2.4.5 causes PermGen build errors on Java 7

[philwebb]

Due to #4209 we didn't notice this at the time of the upgrade but it appears that Groovy 2.4.5 is causing OutOfMemory errors when building the CLI. Rolling back to 2.4.4 locally seems to fix the issue.

[philwebb]

Failing build example here: https://build.spring.io/browse/BOOT-PUB3-164/log

[wilkinsona]

We decided to stick with 2.4.4 for 1.2.7.