fix(linux): deprecate unity-launch flag (#1866)

src/insider/resources/linux/code.desktop

@@ -2,7 +2,7 @@
 Name=@@NAME_LONG@@
 Comment=Code Editing. Redefined.
 GenericName=Text Editor
-Exec=@@EXEC@@ --unity-launch %F
+Exec=@@EXEC@@ %F
 Icon=@@ICON@@
 Type=Application
 StartupNotify=false

src/stable/resources/linux/code.desktop

@@ -2,7 +2,7 @@
 Name=@@NAME_LONG@@
 Comment=Code Editing. Redefined.
 GenericName=Text Editor
-Exec=@@EXEC@@ --unity-launch %F
+Exec=@@EXEC@@ %F
 Icon=@@ICON@@
 Type=Application
 StartupNotify=false