revert default vsync mode to Fifo (#1416)

the mailbox option doesn't do framelimiting on some devices. we need to rely on vsync for framelimiting until bevy supports framelimiting internally. #1343

crates/bevy_wgpu/src/wgpu_type_converter.rs

@@ -640,7 +640,7 @@ impl WgpuFrom<&Window> for wgpu::SwapChainDescriptor {
  width: window.physical_width(),
  height: window.physical_height(),
  present_mode: if window.vsync() {
- wgpu::PresentMode::Mailbox
+ wgpu::PresentMode::Fifo
  } else {
  wgpu::PresentMode::Immediate
  },