Revert "Hide resize grip on gtk2/3 windows when the window is tiled - it makes"

This reverts commit 6f67cf3cd822111041756dd6fff97e94cd4f4c65.

This fixes the bug portion of: https://github.com/linuxmint/muffin/issues/151
keybindings: Fix wrong reaction to tiling hotkeys when a window is maximized.

Fixes #150