Swap NewlineBelow and NewlineAbove bindings for default linux keymap (#36939)

Closes https://github.com/zed-industries/zed/issues/33725

The default bindings for the `editor::NewlineAbove` and
`editor::NewlineBelow` actions in the default keymap were accidentally
swapped some time ago. This causes confusion, as normally these are the
other way around.

This PR fixes this by swapping these back, which also matches what
[VSCode does by
default](https://code.visualstudio.com/shortcuts/keyboard-shortcuts-linux.pdf).

Release Notes:

- Swapped the default bindings for `editor::NewlineBelow` and
`editor::NewlineAbove` for Linux and Windows to align more with other
editors.

assets/keymaps/default-linux.json

@@ -130,8 +130,8 @@
     "bindings": {
       "shift-enter": "editor::Newline",
       "enter": "editor::Newline",
-      "ctrl-enter": "editor::NewlineAbove",
-      "ctrl-shift-enter": "editor::NewlineBelow",
+      "ctrl-enter": "editor::NewlineBelow",
+      "ctrl-shift-enter": "editor::NewlineAbove",
       "ctrl-k ctrl-z": "editor::ToggleSoftWrap",
       "ctrl-k z": "editor::ToggleSoftWrap",
       "find": "buffer_search::Deploy",

assets/keymaps/default-windows.json

@@ -134,8 +134,8 @@
     "bindings": {
       "shift-enter": "editor::Newline",
       "enter": "editor::Newline",
-      "ctrl-enter": "editor::NewlineAbove",
-      "ctrl-shift-enter": "editor::NewlineBelow",
+      "ctrl-enter": "editor::NewlineBelow",
+      "ctrl-shift-enter": "editor::NewlineAbove",
       "ctrl-k ctrl-z": "editor::ToggleSoftWrap",
       "ctrl-k z": "editor::ToggleSoftWrap",
       "find": "buffer_search::Deploy",