Comment on source of ctrl-m in keymaps (#35273)

Closes https://github.com/zed-industries/zed/issues/23896

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -495,7 +495,7 @@
       "shift-f12": "editor::GoToImplementation",
       "alt-ctrl-f12": "editor::GoToTypeDefinitionSplit",
       "alt-shift-f12": "editor::FindAllReferences",
-      "ctrl-m": "editor::MoveToEnclosingBracket",
+      "ctrl-m": "editor::MoveToEnclosingBracket", // from jetbrains
       "ctrl-|": "editor::MoveToEnclosingBracket",
       "ctrl-{": "editor::Fold",
       "ctrl-}": "editor::UnfoldLines",

assets/keymaps/default-macos.json

@@ -549,7 +549,7 @@
       "alt-cmd-f12": "editor::GoToTypeDefinitionSplit",
       "alt-shift-f12": "editor::FindAllReferences",
       "cmd-|": "editor::MoveToEnclosingBracket",
-      "ctrl-m": "editor::MoveToEnclosingBracket",
+      "ctrl-m": "editor::MoveToEnclosingBracket", // From Jetbrains
       "alt-cmd-[": "editor::Fold",
       "alt-cmd-]": "editor::UnfoldLines",
       "cmd-k cmd-l": "editor::ToggleFold",