fix typo in env variable

Author: graemerocher

grails-gradle-plugin/src/main/groovy/org/grails/gradle/plugin/publishing/GrailsCentralPublishGradlePlugin.groovy

@@ -184,7 +184,7 @@ The values can also be placed in PROJECT_HOME/gradle.properties or USER_HOME/gra
         def grailsCentralUsername = System.getenv('GRAILS_CENTRAL_USERNAME') ?: project.hasProperty('grailsCentralUsername') ? project.grailsCentralUsername : ''
         def grailsCentralPassword = System.getenv("GRAILS_CENTRAL_PASSWORD") ?: project.hasProperty('grailsCentralPassword') ? project.grailsCentralPassword : ''
         def grailsPortalUsername = System.getenv('GRAILS_PORTAL_USERNAME') ?: project.hasProperty('grailsPortalUsername') ? project.grailsPortalUsername : ''
-        def grailsPortalPassword = System.getenv("GRAILS_PORTALL_PASSWORD") ?: project.hasProperty('grailsPortalPassword') ? project.grailsPortalPassword : ''
+        def grailsPortalPassword = System.getenv("GRAILS_PORTAL_PASSWORD") ?: project.hasProperty('grailsPortalPassword') ? project.grailsPortalPassword : ''
 
         project.plugins.apply(BintrayPlugin)