x11-toolkits/granite: unbreak build with vala 0.36

/wrkdirs/usr/ports/x11-toolkits/granite/work/granite-0.4.0.1/lib/Widgets/ContractorView.vala:184.27-184.28: error: Argument 1: Cannot pass value to reference or output parameter

	            list.remove (it);
	                         ^^

PR: 222035
Submitted by: cpm