docs: remove unused Desktop Environment Integration doc (#30618)

* docs: remove unused Desktop Environment Integration doc

* Update docs/api/app.md

Co-authored-by: Mark Lee <malept@users.noreply.github.com>

* Update docs/api/app.md

Co-authored-by: Mark Lee <malept@users.noreply.github.com>

Co-authored-by: Erick Zhao <erick@hotmail.ca>
Co-authored-by: Mark Lee <malept@users.noreply.github.com>

docs/api/app.md

@@ -1193,8 +1193,8 @@ badge.
 
 On macOS, it shows on the dock icon. On Linux, it only works for Unity launcher.
 
-**Note:** Unity launcher requires the existence of a `.desktop` file to work,
-for more information please read [Desktop Environment Integration][unity-requirement].
+**Note:** Unity launcher requires a `.desktop` file to work. For more information,
+please read the [Unity integration documentation][unity-requirement].
 
 ### `app.getBadgeCount()` _Linux_ _macOS_
 
@@ -1432,8 +1432,8 @@ An `Integer` property that returns the badge count for current app. Setting the
 
 On macOS, setting this with any nonzero integer shows on the dock icon. On Linux, this property only works for Unity launcher.
 
-**Note:** Unity launcher requires the existence of a `.desktop` file to work,
-for more information please read [Desktop Environment Integration][unity-requirement].
+**Note:** Unity launcher requires a `.desktop` file to work. For more information,
+please read the [Unity integration documentation][unity-requirement].
 
 **Note:** On macOS, you need to ensure that your application has the permission
 to display notifications for this property to take effect.
@@ -1461,7 +1461,7 @@ A `Boolean` property that returns  `true` if the app is packaged, `false` otherw
 [LSCopyDefaultHandlerForURLScheme]: https://developer.apple.com/library/mac/documentation/Carbon/Reference/LaunchServicesReference/#//apple_ref/c/func/LSCopyDefaultHandlerForURLScheme
 [handoff]: https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/Handoff/HandoffFundamentals/HandoffFundamentals.html
 [activity-type]: https://developer.apple.com/library/ios/documentation/Foundation/Reference/NSUserActivity_Class/index.html#//apple_ref/occ/instp/NSUserActivity/activityType
-[unity-requirement]: ../tutorial/desktop-environment-integration.md#unity-launcher
+[unity-requirement]: https://help.ubuntu.com/community/UnityLaunchersAndDesktopFiles#Adding_shortcuts_to_a_launcher
 [mas-builds]: ../tutorial/mac-app-store-submission-guide.md
 [Squirrel-Windows]: https://github.com/Squirrel/Squirrel.Windows
 [JumpListBeginListMSDN]: https://msdn.microsoft.com/en-us/library/windows/desktop/dd378398(v=vs.85).aspx

spec/ts-smoke/electron/main.ts

@@ -172,7 +172,6 @@ app.whenReady().then(() => {
 app.getLocale()
 
 // Desktop environment integration
-// https://github.com/electron/electron/blob/master/docs/tutorial/desktop-environment-integration.md
 
 app.addRecentDocument('/Users/USERNAME/Desktop/work.type')
 app.clearRecentDocuments()