manifest.json: Don't make suggested keyboard shortcut Mac-specificfix-windows-MacCtrl-shortcut-bug

Use a non-Mac shortcut by default and designate the previously-used
shortcut as the default on Mac.

This change attempts to fix an error when installing the extension on
Windows:

    Package is invalid. Details: 'Invalid value for 'commands[1].default': MacCtrl+L.'.

1 files changed, 2 insertions, 1 deletions

diff --git a/manifest.json b/manifest.json
index 827cc1a..1561978 100644
--- a/manifest.json
+++ b/manifest.json
@@ -33,7 +33,8 @@
 	"commands": {
 		"download": {
 			"suggested_key": {
-				"default": "MacCtrl+L"
+				"default": "Alt+L",
+				"mac": "MacCtrl+L"
 			},
 			"description": "Download URL file"
 		}