Use Cancel because that's available in IViewModel...

and we can standardize on Cancel for everything.

Author: shana

src/GitHub.VisualStudio/UI/Views/PullRequestCreationView.xaml

@@ -302,7 +302,7 @@
                                     HorizontalAlignment="Right"
                                     Content="Cancel"
                                     Style="{StaticResource GitHubVsButton}"
-                                    Command="{Binding CancelCommand}"/>
+                                    Command="{Binding Cancel}"/>
                             <Button HorizontalAlignment="Right" Margin="6,0,0,0" Content="Create pull request" Grid.Column="1" Style="{StaticResource GitHubVsPrimaryActionButton}" />
                         </Grid>
                     </StackPanel>