docs: Fix a few typos (#5655)

There are small typos in:
- closure/goog/base.js
- core/contextmenu_items.js
- core/insertion_marker_manager.js
- core/toolbox/collapsible_category.js
- demos/blockfactory/workspacefactory/wfactory_controller.js
- demos/blockfactory/workspacefactory/wfactory_view.js
- tests/mocha/field_colour_test.js

Fixes:
- Should read `updates` rather than `udpates`.
- Should read `unhighlighting` rather than `unhiglighting`.
- Should read `then` rather than `tehn`.
- Should read `modified` rather than `modifed`.
- Should read `different` rather than `diffferent`.
- Should read `currently` rather than `currenly`.
- Should read `browser` rather than `broswer`.

demos/blockfactory/workspacefactory/wfactory_controller.js

@@ -75,7 +75,7 @@ WorkspaceFactoryController = function(toolboxName, toolboxDiv, previewDiv) {
 // toolbox.
 WorkspaceFactoryController.MODE_TOOLBOX = 'toolbox';
 // Pre-loaded workspace editing mode. Changes the user makes to the workspace
-// udpates the pre-loaded blocks.
+// updates the pre-loaded blocks.
 WorkspaceFactoryController.MODE_PRELOAD = 'preload';
 
 /**

demos/blockfactory/workspacefactory/wfactory_view.js

@@ -333,7 +333,7 @@ WorkspaceFactoryView.prototype.unmarkShadowBlock = function(block) {
 };
 
 /**
- * Sets the tabs for modes according to which mode the user is currenly
+ * Sets the tabs for modes according to which mode the user is currently
  * editing in.
  * @param {string} mode The mode being switched to
  *   (WorkspaceFactoryController.MODE_TOOLBOX or WorkspaceFactoryController.MODE_PRELOAD).