Remove 'v' menu keys

We can no longer use this because 'v' is globally reserved for range select.
Conveniently it was the first item in the menu anyway for both of these.

pkg/gui/controllers/branches_controller.go

@@ -165,7 +165,6 @@ func (self *BranchesController) viewUpstreamOptions(selectedBranch *models.Branc
 				ShowBranchHeads:         false,
 			})
 		},
-		Key: 'v',
 	}
 
 	unsetUpstreamItem := &types.MenuItem{