Change spawn instance modifier to Shift

The shortcut Ctrl+Return was often accidentaly hit.

Install/Templates/alacritty/alacritty.yml

@@ -122,7 +122,7 @@ key_bindings:
   - { key: PageDown,  mods: Shift,   action: ScrollPageDown, mode: ~Alt       }
   - { key: Home,      mods: Shift,   action: ScrollToTop,    mode: ~Alt       }
   - { key: End,       mods: Shift,   action: ScrollToBottom, mode: ~Alt       }
-  - { key: Return,    mods: Control, action: SpawnNewInstance }
+  - { key: Return,    mods: Shift, action: SpawnNewInstance }
 
 debug:
   render_timer: false