rename group command to groups to have consistency into the cli

tests/test_cli.py

@@ -162,7 +162,7 @@ def test_group_count_multi_browser_shows_total():
             BrowserTarget("work", "work", "/tmp/work.sock"),
         ],
     ), patch("browser_cli.commands.groups.send_command", side_effect=fake_send_command):
-        result = CliRunner().invoke(main, ["group", "count"])
+        result = CliRunner().invoke(main, ["groups", "count"])
 
     assert result.exit_code == 0
     assert "Browser" in result.output
@@ -175,7 +175,7 @@ def test_group_list_leaves_unnamed_group_cell_empty():
         "browser_cli.commands.groups.send_command",
         return_value=[{"id": 42, "title": "", "color": "grey", "collapsed": False, "tabCount": 1}],
     ):
-        result = CliRunner().invoke(main, ["group", "list"])
+        result = CliRunner().invoke(main, ["groups", "list"])
 
     assert result.exit_code == 0
     assert "(unnamed)" not in result.output