Solving Groovy compiler in GGTS (Groovy: compiler mismatch)

Hello world,

So I was trying to run a Grails 2.3.5 project in my recently installed GGTS 3.4, and I was getting the next error:

Description    Resource    Path    Location    Type
Groovy: compiler mismatch Project level is: 2.1 Workspace level is 2.0
Groovy compiler level expected by the project does not match workspace compiler level.

I couldn't find the Groovy Compiler 2.1 and didn't know how to install it. Here is how you do it:
"...To install the Groovy 2.1 compiler in GGTS, first click on the Dashboard tab. If it is not visible, goto Help -> Dashboard. at the bottom left of the window, click Extensions. Scroll down the list and check Groovy 2.1 Compiler for Groovy-Eclipse. Then click Install on the lower right of the window. Follow the defaults to install, and it will configure itself. I have found it cumbersome to get existing projects to fully correct themselves, so I usually just delete the project and recreate it." ~Mike Kelly (Taken from: http://www.grailsexample.net/course-outline/)

Then, the next projects I created with Grails 2.3.5 didn't give me any more errors about the Groovy Compiler