GT Inspector: Fix Hook for Unary Presentation Generator

This code is (probably only) used by Magritte to declaratively create GT Inspector presentations. I (@seandenigris) [originally introduced it](moosetechnology/Moose#1130), but it seems to have been altered (I'm assuming accidentally, possibly as a result of a system-wide method rename, but can't tell for sure because the change seems to predate the move to GH).

Author: seandenigris

src/GT-Inspector/ProtoObject.extension.st

@@ -59,7 +59,7 @@ ProtoObject >> gtInspectorPresentationsFromPragmas: aCollection In: composite in
 		do: [ :eachPragma | 
 			eachPragma methodSelector numArgs = 0
 				ifTrue: [ | presentationSource |
-					presentationSource := self perform: eachPragma selector.
+					presentationSource := self perform: eachPragma methodSelector.
 					presentationSource glmPresentation
 						cull: composite
 						cull: aGTInspector