run linters for plugin builds

flag = none

Test:
- Jenkins passes
- plugin build with this gerrit passes

Change-Id: I67838ae08cb2443c3c41fdcce157a83027e43243
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/251652
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: James Butters <jbutters@instructure.com>
Product-Review: James Butters <jbutters@instructure.com>
Reviewed-by: Aaron Ogata <aogata@instructure.com>
Reviewed-by: Kyle Rosenbaum <krosenbaum@instructure.com>
Reviewed-by: Andrea Cirulli <andrea.cirulli@instructure.com>

Jenkinsfile

@@ -538,7 +538,7 @@ pipeline {
                   }
                 }
 
-                if (!configuration.isChangeMerged() && env.GERRIT_PROJECT == 'canvas-lms') {
+                if (!configuration.isChangeMerged()) {
                   echo 'adding Linters'
                   timedStage('Linters', stages, {
                     skipIfPreviouslySuccessful("linters") {