Fix misspelling error

Change-Id: I318f3021e7118605186f1d1bfd15bbe54fd40e8b

gr-resemble-diff-mode/gr-resemble-diff-mode.js

diff --git a/gr-resemble-diff-mode/gr-resemble-diff-mode.js b/gr-resemble-diff-mode/gr-resemble-diff-mode.js
index 1c9076e..50661b8 100644
--- a/gr-resemble-diff-mode/gr-resemble-diff-mode.js
+++ b/gr-resemble-diff-mode/gr-resemble-diff-mode.js
@@ -19,7 +19,7 @@
 
     properties: {
       baseImage: Object,
-      revisonImage: Object,
+      revisionImage: Object,
     },
 
     observers: [